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Machines Sous 24 Telecharger Jeux De Casino 92
The Component Parts of a Savage Beating PDF generated using the open source mwlib toolkit. See http://code.pediapress.com/ for more information. PDF generated at: Thu, 07 Jul 2011 17:06:31 UTC Contents Articles Antenna (biology) 1 Arm 4 Basting (cooking) 6 Digit (anatomy) 8 Duct (HVAC) 10 Ear 15 Eye 23 Fork 35 Gill 39 Grater 43 Handle (grip) 45 Head 47 Hoof 49 Horn (anatomy) 50 Human leg 54 Knee 68 Ladle (spoon) 80 Meat slicer 81 Nail (anatomy) 82 Peel (tool) 88 Scraper (kitchen) 89 Skin 92 Spatula 97 Tongs 98 Wedge (mechanical device) 99 Zester 101 References Article Sources and Contributors 102 Image Sources, Licenses and Contributors 107 Article Licenses License 110 Antenna (biology) 1 Antenna (biology) Antennae (singular: antenna) in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes. In arthropods, antennae are connected to the front-most segments. In crustaceans, they are biramous and present on the first two segments of the head, with the smaller pair known as antennules. All other arthropod groups, except chelicerates, proturans and arachnids which have none, have a single, uniramous pair of antennae. These antennae Electron micrograph of antenna surface detail of a are jointed, at least at the base, and generally extend forward from the wasp (Vespula vulgaris) head. They are sensory organs, although the exact nature of what they sense and how they sense it is not the same in all groups, nor always clear. Functions may variously include sensing touch, air motion, heat, vibration (sound), and especially olfaction (smell) or gustation (taste). Insects Antennae are the primary olfactory sensors of insects[1] and are accordingly well-equipped with a wide variety of sensilla (singular: sensillum). Paired, mobile, and segmented, they are located between the eyes on the forehead. Embryologically, they represent the appendages of the second head segment.[2] All insects have antenna though these may be greatly reduced in the larval forms. Amongst the non-insect classes of Hexapoda, Collembola and Diplura have antenna, but Protura do not.[3] Terms used to describe antennae shapes Structure The three basic segments of the typical insect antenna are the scape (base), the pedicel (stem), and finally the flagellum, which often comprises many units known as flagellomeres.[4] The number of flagellomeres can vary greatly, and is often of diagnostic importance. True flagellomeres have a membranous articulation between them, but in many insects, especially the more primitive groups, the flagellum is entirely or partially composed of a flexible series of small annuli, which are not true flagellomeres.[4] Antennal shape in the Lepidoptera from C. T. Bingham (1905) In many beetles and in the chalcidoid wasps, the apical flagellomeres form a club, and the collective term for the segments between the club and the antennal base is the funicle; for traditional reasons, in beetles it is the segments between the club and the scape, but in wasps, it is the segments between the club and the pedicel.[4] In the groups with more uniform antennae (for example: Diplopoda), all segments are called antennomeres. Some groups have a simple or variously modified apical or subapical bristle called an arista (this may be especially well-developed in various Diptera).[5] Antenna (biology) 2 Functions Olfactory receptors on the antennae bind to free-floating molecules, such as water vapour, and odours including pheromones. The neurons that possess these receptors signal this binding by sending action potentials down their axons to the antennal lobe in the brain. From there, neurons in the antennal lobes connect to mushroom bodies that identify the odour. The sum of the electrical potentials of the antenna to a given odour can be measured using an electroantennogram.[6] In the case of the Monarch butterfly, it has been shown that antennae are necessary for proper time-compensated solar compass orientation during migration, that antennal clocks exist in monarchs, and that they are likely to provide the primary timing mechanism for Sun compass orientation.[7] Crustaceans Crustaceans bear two pairs of antennae. The first pair are uniramous and are often referred to as antennules, while the second pair are biramous, meaning that each antenna is composed of two parts, joined at their base .[8] In most adults, the antenna are sensory organs, but they are used by the nauplius larva for swimming. In some groups of crustaceans, such as the spiny lobsters and slipper lobsters, the second antennae are enlarged, while in others, such as crabs, the antennae are reduced in size. A spiny lobster, showing the enlarged second antennae The large flattened plates in front of the eyes of a slipper lobster are the modified second antennae. The crab Cancer pagurus, showing its reduced antennae Antenna (biology) 3 Antennules of the Caribbean hermit crab Cellular antennae Within the biological and medical disciplines, recent discoveries have noted that primary cilia in many types of cells within eukaryotes serve as cellular antennae. These cilia play important roles in chemosensation, mechanosensation, and thermosensation. The current scientific understanding of primary cilia organelles views them as "sensory cellular antennae that coordinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation."[9] "Almost every vertebrate cell has a specialized cell surface projection called a primary cilium. …primary cilia are key participants in Structural diagram of a single cilium extending intercellular signaling. This new appreciation of primary cilia as into extra-cellular space cellular antennae that sense a wide variety of signals could help explain why ciliary defects underlie such a wide range of human disorders, including retinal degeneration, polycystic kidney disease, Bardet-Biedl syndrome, and neural tube defects."[10] References [1] Darby, Gene (1958). What is a butterfly?. Chicago: Benefic Press. p. 8. OCLC 1391997. [2] Gullan, Penny J.; Cranston, Peter S. (2005). The Insects: an Outline of Entomology (3rd ed.). Oxford, UK: Blackwell Publishing. p. 38. ISBN 1-4051-1113-5. [3] Chapman, Reginald Frederick (1998). The Insects: Structure and Function (4th ed.). New York: Cambridge University Press. p. 8. ISBN 0-521-57890-6. [4] Thomas A. Keil (1999). "Morphology and development of the peripheral olfactory organs". In Hansson, Bill S.. Insect Olfaction (1st ed.). Springer. pp. 5–48. ISBN 978-3540650348. [5] Lawrence, Eleanor, ed (2005). Henderson's Dictionary of Biological Terms (13th ed.). Pearson Education. p. 51. ISBN 978-0-13-127384-9. [6] "Electroantennography (EAG)" (http:/ / www. uni-goettingen. de/ en/ 71544. html). Georg-August-Universität Göttingen. . Retrieved March 27, 2010. [7] Merlin, Christine; Gegear, Robert J.; Reppert, Steven M. (September 2009). "Antennal circadian clocks coordinate sun compass orientation in migratory monarch butterflies". Science 325 (5948): 1700–1704. doi:10.1126/science.1176221. PMC 2754321. PMID 19779201. [8] "Superphylum Arthropoda" (http:/ / www. geo. arizona. edu/ geo3xx/ geo308_fall2002/ 6arthropods. htm). University of Arizona. . [9] Satir, Peter; Christensen, Søren T. (June 2008). "Structure and function of mammalian cilia". Histochemistry and Cell Biology 129 (6): 687–693. doi:10.1007/s00418-008-0416-9. PMC 2386530. PMID 18365235. [10] Singla, Veena; Reiter, Jeremy F. (August 2006). "The primary cilium as the cell's antenna: signaling at a sensory organelle". Science 313 (5787): 629–633. doi:10.1126/science.1124534. PMID 16888132. Arm 4 Arm Arm The human arm Cross-section through the middle of upper arm. Latin brachium In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods. In anatomical usage, the term arm refers specifically to the segment between the shoulder and the elbow,[1] [2] while the segment between the elbow and wrist is the forearm. However, in common, literary, and historical usage, arm refers to the entire upper limb from shoulder to wrist. This article uses the former definition; see upper limb for the wider definition. In primates the arm is adapted for precise positioning of the hand and thus assist in the hand's manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the structure of the two forearm bones which can rotate around each other allows for additional range of motion at that level. Skeleton The humerus is the bone of the arm. It joins with the scapula above in the shoulder at the glenohumeral joint and with the ulna and radius below at the elbow. The elbow joint is the hinge joint between the distal end of the humerus and the proximal ends of the radius and ulna. The humerus cannot be broken easily. Its strength allows it to handle loading up to 300 pounds (140 kg). Muscles The arm is divided by a fascial layer (known as lateral and medial intermuscular septa) separating the muscles into two osteofascial Bone structure of a human arm. compartments: the anterior and the posterior compartments of the arm. The fascia merges with the periosteum (outer bone layer) of the humerus. The compartments contain muscles which are innervated by the same nerve and perform the same action. Two other muscles are considered to be partially in the arm: Arm 5 • The large deltoid muscle is considered to have part of its body in the anterior compartment. This muscle is the main abductor muscle of the upper limb and extends over the shoulder. • The brachioradialis muscle originates in the arm but inserts into the forearm. This muscle is responsible for rotating the hand so its palm faces forward (supination). Nerve and blood supply The cubital fossa (colloquially known as the elbow pit) is clinically important for venepuncture and for blood pressure measurement. Innervation The musculocutaneous nerve, from C5, C6, C7, is the main supplier of muscles of the anterior compartment. It originates from the lateral cord of the brachial plexus of nerves. It pierces the coracobrachialis muscle and gives off branches to the muscle, as well as to brachialis and biceps brachii. It terminates as the anterior cutaneous nerve of the forearm. The radial nerve, which is from the fifth cervical spinal nerve to the first thoracic spinal nerve, originates as the continuation of the posterior cord of the brachial plexus. This nerve enters the lower triangular space (an imaginary space bounded by, amongst others, the shaft of the humerus and the triceps brachii) of the arm and lies deep to the triceps brachii. Here it travels with a deep artery of the arm (the profunda brachii), which sits in the radial groove of the humerus. This fact is very important clinically as a fracture of the bone at the shaft of the bone here can cause lesions or even transections in the nerve. Cutaneous innervation of the right upper extremity. Other nerves passing through give no supply to the arm. These include: • The median nerve, nerve origin C5-T1, which is a branch of the lateral and medial cords of the brachial plexus. This nerve continues in the arm, travelling in a plane between the biceps and triceps muscles. At the cubital fossa, this nerve is deep to the pronator teres muscle and is the most medial structure in the fossa. The nerve passes into the forearm. • The ulnar nerve, origin C8-T1, is a continuation of the medial cord of the brachial plexus. This nerve passes in the same plane as the median nerve, between the biceps and triceps muscles. At the elbow, this nerve travels posterior to the medial epicondyle of the humerus. This means that condylar fractures can cause lesion to this nerve. Arteries The main artery in the arm is the brachial artery. This artery is a continuation of the axillary artery. The point at which the axillary becomes the brachial is distal to the lower border of teres major. The brachial artery gives off an important branch, the profunda brachii (deep artery of the arm). This branching occurs just below the lower border of teres major. Main arteries of the arm. Arm 6 The brachial artery continues to the cubital fossa in the anterior compartment of the arm. It travels in a plane between the biceps and triceps muscles, the same as the median nerve and basilic vein. It is accompanied by venae comitantes (accompanying veins). It gives branches to the muscles of the anterior compartment. The artery is in between the median nerve and the tendon of the biceps muscle in the cubital fossa. It then continues into the forearm. The profunda brachii travels through the lower triangular space with the radial nerve. From here onwards it has an intimate relationship with the radial nerve. They are both found deep to the triceps muscle and are located on the spiral groove of the humerus. Therefore fracture of the bone may not only lead to lesion of the radial nerve, but also haematoma of the internal structures of the arm. The artery then continues on to anastamose with the recurrent radial branch of the brachial artery, providing a diffuse blood supply for the elbow joint. Veins The veins of the arm carry blood from the extremities of the limb, as well as drain the arm itself. The two main veins are the basilic and the cephalic veins. There is a connecting vein between the two, the median cubital vein, which passes through the cubital fossa and is clinically important for venepuncture (withdrawing blood). The basilic vein travels on the medial side of the arm and terminates at the level of the seventh rib. The cephalic vein travels on the lateral side of the arm and terminates as the axillary vein. It passes through the deltopectoral triangle, a space between the deltoid and the pectoralis major muscles. References [1] " arm (http:/ / www. mercksource. com/ pp/ us/ cns/ cns_hl_dorlands_split. jsp?pg=/ ppdocs/ us/ common/ dorlands/ dorland/ one/ 000007845. htm)" at Dorland's Medical Dictionary [2] MeSH Arm (http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2011/ MB_cgi?mode=& term=Arm) Basting (cooking) Basting is a cooking technique that involves cooking meat with either its own juices or some type of preparation such as a sauce or marinade. The meat is left to cook, then periodically coated with the juice. Prominently used in grilling, rotisserie, roasting, and other meat preparations where the meat is over heat for extended periods of time, basting is used to keep meat moist during the cooking process and also to apply or enhance flavor. Improperly administered basting, however, may actually lead to the very problem it is designed to prevent: the undesired loss of moisture (drying out) of the meat. If not compensated by countermeasures, the opening of the oven door and the resulting loss of temperature and moisture content of the air circulating inside can lead to increased evaporation from the meat surfaces. In the case of tough meats such as beef, bison, and deer, the result can be a hardened, shell-like, overcooked or burned outer crust, while inner layers of the meat may still be undercooked or raw; with soft meats such as poultry, the result can be a thorough drying from the surface to the bone, as in the case of the traditional American turkey. Basting a turkey with a turkey baster Basting (cooking) To prevent this, the easiest solution is to place the meat in a closed oven bag, which traps evaporating moisture and does not let it disseminate into the oven space and then out to the kitchen. The meat is "auto basted" when the air trapped inside the bag reaches the point of its maximum possible moisture content, and the resulting precipitate forms into drops on the surfaces of the meat or the wall of the bag. The drops roll down to the lowest point of the closed space, where the meat sits and cooks in the resulting juices. This technique often requires very minimal or no added liquids other than what the meat already contains, for loss of moisture is virtually negligible from inside the bag. However, oven bags lose their advantage if they are opened even one time during the cooking process, and seasoned cooks, who prefer adding flavoring, natural oils (herbs), or aromatics in different times and portions during the process, generally use alternate practices to avoid drying out the meat. For instance, they allow extended cooking time, administer increased amounts of juices, coat the meat with moisture rich fruits or fat-rich cuts, such as bacon, or actual fat, place moisture rich fruits and vegetables around the cooking meats, and if possible, use a convection oven. This is a type of cooking usually recommended for dishes that generally taste mild, but are served with sauces that provide complimenting or overpowering flavor to them, for example Chicken chasseur. Basting is a technique generally known to be used for turkey, pork, chicken, duck, and beef (including steak), but may be applied to virtually any type of meat. External links How Stuff Works - Basting [1] References [1] http:/ / recipes. howstuffworks. com/ basting-questions. htm 7 Digit (anatomy) 8 Digit (anatomy) A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates. Names Some languages have different names for hand and foot digits (English: respectively "finger" and "toe", French: "doigts" and "orteils"). In other languages, e.g. Russian, Polish, Portuguese, Italian, Czech, Tagalog, Turkish & Persian there are no specific one-word names for fingers and toes; these are called "digit of the hand" or "digit of the foot" instead. Human digits Humans normally have five digits on each extremity. Each digit is formed by several bones called phalanx, surrounded by soft tissues. Every human finger normally has a nail on its distal phalanx. There can be polydactyly number variation and extra fingers can be useful. In one individual with seven fingers, exploited his extra digits and claimed, they “gave him some advantages in playing the piano.”[1] Brain representation Each finger has an orderly somatotopic representation on the cerebral cortex in the somatosensory cortex area 3b, [2] part of area 1[3] and a distributed, overlapping representations in the supplementary motor area and primary motor area.[4] The somatosensory cortex representation of the hand is a dynamic reflection of the fingers on the external hand: in syndactyly people have a clubhand of webbed, shortened fingers. However, not only are the fingers of their hands fused, but the cortical maps of their individual fingers also form a club hand. The fingers can be surgically divided to make a more useful hand. Surgeons did this at the Institute of Reconstructive Plastic Surgery in New York to a 32-year-old man with the initials O. G.. They touching O. G.’s fingers before and after surgery while using MRI brain scans. Before the surgery, the fingers mapped onto his brain were fused close together; afterward, the maps of his individual fingers did indeed separate and take the layout corresponding to a normal hand.[5] Evolution Two ideas about the homology of arms, hands and digits have existed in the past 130 years. First that digits are unique to tetrapods[6] [7] and second that antecedents were present in the fins of early sarcopterygian fish.[8] Until recently it was concluded that "Both genetic and fossil data support the hypothesis that digits are evolutionary novelties".[9] p. 640. A reconstruction of a Panderichthys However new research that has created a three-dimensional reconstruction of a Panderichthys, a coastal fish from the Devonian period 385 million years ago, shows that these animals already had many of the homologous bones present in the forelimbs of limbed vertebrates.[10] For example, they had "radial" bones similar to rudimentary fingers but positioned in the arm-like base of their fins.[10] Thus there was in the evolution of tetrapods a shift such that the outermost part of the fins were lost and came to be replaced by early digits. This change is consistent with additional evidence from the study of actinopterygians, sharks and lungfish that the digits of tetrapods arose from pre-existing distal radials present in more primitive fish.[10] [11] Digit (anatomy) Controversy still exists since Tiktaalik, a vertebrate often considered to be the missing link between fishes and land-living animals, had stubby leg-like limbs that lacked the finger-like radial bones found in the Panderichthys. The researchers of the paper commented that "It is difficult to say whether this character distribution implies that Tiktaalik is autapomorphic, that Panderichthys and tetrapods are convergent, or that Panderichthys is closer to tetrapods than Tiktaalik. At any rate, it demonstrates that the fish–tetrapod transition was accompanied by significant character incongruence in functionally important structures.".[10] p. 638. Bird and theropod dinosaur digits Birds and theropod dinosaurs (from which birds evolved) have three digits on their hands. Paradoxically the two digits that are missing are different: the bird hand (embedded in the wing) is thought to derive from the second, third and fourth digits of the ancestral five-digit hand. In contrast, the theropod dinosaur seem to be the first, second and third digits. Recently a Jurassic theropod intermediate fossil Limusaurus has been found in the Junggar Basin in western China that has a complex mix: it has a first digit stub and full second, third and fourth digits but its wrist bones are like those that are associated with the second, third and fourth digits while its finger bones are those of the first, second and third digits.[12] This suggests the evolution of digits in birds resulted from a "shift in digit identity characterized early stages of theropod evolution"[12] Notes [1] Dwight T. (1892). Fusion of hands. Memoirs of the Boston Society of Natural History, 4, 473-486. [2] van Westen D, Fransson P, Olsrud J, Rosén B, Lundborg G, Larsson EM. (2004). Fingersomatotopy in area 3b: an fMRI-study (http:/ / www. pubmedcentral. nih. gov/ picrender. fcgi?artid=517711& blobtype=pdf). BMC Neurosci. 5:28. PMID 15320953 [3] Nelson AJ, Chen R. (2008). Digit somatotopy within cortical areas of the postcentral gyrus in humans. Cereb Cortex. 18(10):2341-51. PMID 18245039 [4] Kleinschmidt A, Nitschke MF, Frahm J. (1997). Somatotopy in the human motor cortex hand area. A high-resolution functional MRI study. Eur J Neurosci. 9(10):2178-86. PMID 9421177 [5] Mogilner A, Grossman JA, Ribary U, Joliot M, Volkmann J, Rapaport D, Beasley RW, Llinás RR. (1993). Somatosensory cortical plasticity in adult humans revealed by magnetoencephalography (http:/ / www. pubmedcentral. nih. gov/ picrender. fcgi?artid=46347& blobtype=pdf). Proc Natl Acad Sci U S A. 90(8):3593-7. PMID 8386377 [6] Holmgren N. (1933). On the origin of the tetrapod limb. Acta Zoologica 14, 185–295. [7] Vorobyeva EI.(1992). The role of development and function in formation of tetrapod like pectoral fins. Zh. Obshch. Biol. 53, 149–158. [8] Watson DMS. (1913). On the primitive tetrapod limb. Anat. Anzeiger 44, 24–27. [9] Shubin N, Tabin C, Carroll S. (1997). Fossils, genes and the evolution of animal limbs. Nature. 388(6643):639-48. doi:10.1038/41710 PMID 9262397 [10] Boisvert CA, Mark-Kurik E, Ahlberg PE. (2008). The pectoral fin of Panderichthys and the origin of digits. Nature. 456(7222):636-8. PMID 18806778 [11] Than, Ker (September 24, 2008). "Ancient Fish Had Primitive Fingers, Toes" (http:/ / news. nationalgeographic. com/ news/ 2008/ 09/ 080924-fish-fingers. html?source=rss). National Geographic News. . [12] Xing Xu et al.(2009). A Jurassic ceratosaur from China helps clarify avian digital homologies. Nature 459: 940-944 doi:10.1038/nature08124 9 Duct (HVAC) 10 Duct (HVAC) Ducts are used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air.[1] Ducts also deliver, most commonly as part of the supply air, ventilation air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort. A duct system is often called ductwork. Planning ('laying out'), sizing, optimizing, detailing, and finding the pressure losses through a duct system is called duct design.[2] A round galvanized steel duct connecting to a typical diffuser Materials Ducts can be made out of the following materials: Galvanized mild steel is the standard and most common material used in fabricating ductwork. Polyurethane and Phenolic insulation panels (pre-insulated air ducts) Traditionally, air ductwork is made of sheet metal which is installed first and then lagged with insulation as a secondary operation. Ductwork manufactured from rigid insulation panels does not need any further insulation and is installed in a single fix. Light weight and installation speed are among the features of preinsulated aluminium ductwork, also custom or special shapes of ducts can be easily fabricated in the shop or on site. Fire-resistance rated mechanical shaft with HVAC sheet metal ducting and copper piping, as well as "HOW" (Head-Of-Wall) joint between top of concrete block wall and underside of concrete slab, firestopped with ceramic fibre-based firestop caulking on top of rockwool. The ductwork construction starts with the tracing of the duct outline onto the aluminium preinsulated panel, then the parts are typically cut at 45 degree, bent if required to obtain the different fittings (i.e. elbows, tapers) and finally assembled with glue. Aluminium tape is applied to all seams where the external surface of the aluminium foil has been cut. A variety of flanges are available to suit various installation requirements. All internal joints are sealed with sealant. Among the various types of rigid polyurethane foam panels available, a new water formulated panel stands out. In this particular panel, the foaming process is obtained through the use of water instead of the CFC, HCFC, HFC and HC gasses. And most manufacturers of rigid polyurethane foam panels use normal pentane as foaming agent instead of the CFC, HCFC, HFC and HC gasses, so do manufacturers of rigid phenolic foam panels. A rigid phenolic insulation ductwork system is available and complies with the UL 181 standard for class 1 air ductwork. Both polyurethane foam panels and phenolic foam panels are then coated with aluminum sheets on both sides, with outside aluminum thicknesses that can vary from 80 micrometres for indoor use to 200 micrometres for external use or high air pressure in order to guarantee the high mechanical characteristics of the duct, or then coated with aluminum sheets on inside, and coated with 200 micrometres sheet metal or pre-painted sheet metal on outside. Duct (HVAC) Fiberglass duct board (preinsulated non metallic ductwork) Fiberglass duct board panels provide built-in thermal insulation and the interior surface absorbs sound, helping to provide quiet operation of the HVAC system. The duct board is formed by sliding a specially-designed knife along the board using a straightedge as a guide; the knife automatically trims out a "valley" with 45° sides; the valley does not quite penetrate the entire depth of the duct board, providing a thin section that acts as a hinge. The duct board can then be folded along the valleys to produce 90° folds, making the rectangular duct shape in the fabricator's desired size. The duct is then closed with staples and special aluminum or similar 'metal-backed' tape. Commonly available duct tape should not be used on air ducts, metal, fiberglass, or otherwise, that are intended for long-term use; the adhesive on so called 'duct tape' dries and releases with time. Flexible Ducting Flexible ducts, known as flex, have a variety of configurations, but for HVAC applications, they are typically flexible plastic over a metal wire coil to make round, flexible duct. In the United States, the insulation is usually glass wool, but other markets such as Australia, use both polyester fibre and glass wool for thermal insulation. A protective layer surrounds the insulation, and is usually composed of polyethylene or metalised PET. Flexible duct is very convenient for attaching supply air outlets to the rigid ductwork. However, the pressure loss through flex is higher than for most other types of ducts. As such, designers and installers attempt to keep their installed lengths Example of flexible ducting. (runs) short, e.g., less than 15 feet or so, and to minimize turns. Kinks in flex must be avoided. Some flexible duct markets prefer to avoid using flexible duct on the return air portions of HVAC systems, however flexible duct can tolerate moderate negative pressures - the UL181 test requires a negative pressure of 200 Pa.[3] Fabric Fabric ducting, also known as air socks, duct socks or textile ducts, are designed for even air distribution throughout the entire length. Usually made of special polyester material, fabric ducts can provide air to a space more effectively than a conventional exposed duct system. Fabric duct is a misnomer as "fabric duct" is actually an "air distribution device" and is not intended as a conduit (duct) for conditioned air. However, as it often replaces hard or metal ductwork it is easy to perceive it simply as duct. Fabric air dispersion systems, is the more definitive name. As they may be manufactured with venting or orifices for even air distribution along any length of the system, they commonly will provide a more even distribution and blending of the conditioned air in a given space. As "fabric duct" is used for air distribution, textile ducts are not rated for nor should they be used in ceilings or concealed attic spaces. Applications for fabric duct in raise floor applications; however, are available. Depending on the manufacturer, "fabric duct" is available in standard and custom colours with options for silk screening or other forms of appliques. "Fabric duct", depending on the manufacturer, may be available in air permeable(porous) or non-porous fabric. As a benchmark, a designer may make the determination of which fabric is more applicable by asking the question if the application would require insulated metal duct? If metal duct would be insulated in a given application or installation, air permeable fabric would be recommended as it will not commonly create condensation on its surface and can therefore be used where air is to be supplied below the dew point. Again; depending on the material and manufacturer, material that eliminates moisture may also be healthier and may also be provided with an active anti-microbial agent to inhibit bacteria growth. Porous material also tends to require less maintenance as it repels 11 Duct (HVAC) dust and other airborne contaminants. Duct system components Besides the ducts themselves, complete ducting systems contain many other components. Vibration isolators A duct system often begins at an air handler. The blowers in the air handlers can create substantial vibration and the large area of the duct system would transmit this noise and vibration to the inhabitants of the building. To avoid this, vibration isolators (flexible sections) are normally inserted into the duct immediately before and after the air handler. The rubberized canvas-like material of these sections allow the air handler to vibrate without transmitting much vibration to the attached ducts. Take-offs Downstream of the air handler, the supply air trunk duct will commonly fork, providing air to many individual air outlets such as diffusers, grilles, and registers. When the system is designed with a main duct branching into many subsidiary branch ducts, fittings called take-offs allow a small portion of the flow in the main duct to be diverted into each branch duct. Take-offs may be fitted into round or rectangular openings cut into the wall of the main duct. The take-off commonly has many small metal tabs that are then bent to retain the take-off on the main duct; round versions are called spin-in fittings. Other take-off designs use a snap-in attachment method, sometimes coupled with an adhesive foam gasket to provide improved sealing. The outlet of the take-off then connects to the rectangular, oval, or round branch duct. Stacks, boots, and heads Ducts, especially in homes, must often allow air to travel vertically within relatively thin walls. These vertical ducts are called stacks and are formed with either very wide and relatively thin rectangular sections or oval sections. At the bottom of the stack, a stack boot provides a transition from an ordinary large round or rectangular duct to the thin wall-mounted duct. At the top, a stack head can provide a transition back to ordinary ducting while a register head allows the transition to a wall-mounted air register. Volume Control Dampers Ducting systems must often provide a method of adjusting the volume of air flow to various parts of the system. VCDs (Volume Control Dampers - Not To Be confused with Smoke/Fire Dampers) provide this function. Besides the regulation provided at the registers or diffusers that spread air into individual rooms, dampers can be fitted within the ducts themselves. These dampers may be manual or automatic. Zone dampers provide automatic control in simple systems while VAVs allow control in sophisticated systems. Smoke/Fire Dampers Smoke and Fire dampers are found in ductwork, where the duct passes through a firewall or firecurtain. Smoke dampers are automated with the use of a mechanical motor often referred to as an Actuator. A probe connected to the motor is installed in the run of duct, and detects smoke within the duct system which has been extracted from a room, or which is being supplied from the AHU (Air Handling Unit) or elsewhere within the run. Once smoke is detected within the duct, the Actuator triggers the motor release and the smoke damper will automatically close until manually re-opened. You will also find Fire dampers in the same places as smoke dampers, depending on the application of the area after the firewall. Unlike smoke dampers, they are not triggered by any electrical system, which is perfect in the event of 12 Duct (HVAC) an electrical failure where the Smoke dampers would fail to close. A fire damper is held open by a bar crossing the corrigated screen, which will break and allow the damper to close when air in the duct is above a certain temperature. This again will then have to be manually re-opened. Plenums Plenums are the central distribution and collection units for an HVAC system. The return plenum carries the air from several large return grills (vents) to a central air handler. The supply plenum directs air from the central unit to the rooms which the system is designed to heat or cool. Terminal units While single-zone constant air volume systems typically don't have them, other types of air distribution systems often have terminal units in the branch ducts. Usually there is one terminal unit per thermal zone. Some types of terminal units are VAV 'boxes' of either single or dual duct, fan-powered mixing boxes of either parallel or series arrangement, and induction terminal units. Terminal units may also include either, or both, a heating or cooling coil. Air terminals 'Air terminals' are the supply air outlets and 'return' or 'exhaust air inlets'. For supply, diffusers are most common, but grilles, and for very small HVAC systems such as in residences, 'registers' are also used widely. Return or 'exhaust grilles' are used primarily for appearance reasons, but some also incorporate an air filter and are known as 'filter returns'.[4] Duct cleaning The position of the U.S. Environmental Protection Agency (EPA) is that "If no one in your household suffers from allergies or unexplained symptoms or illnesses and if, after a visual inspection of the inside of the ducts, you see no indication that your air ducts are contaminated with large deposits of dust or mold (no musty odor or visible mold growth), having your air ducts cleaned is probably unnecessary."[5] Studies by the EPA and the Canadian Mortgage and Housing Corporation (CMHC) in the 1990s has lead CMHC to conclude that "duct cleaning will not usually change the quality of the air you breathe, nor will it significantly affect airflows or heating costs".[6] Signs and indicators • • • • • • • When cleaning, you need to sweep and dust your furniture more than usual. After cleaning, there's still left over dust floating around the house that you can see. After or during sleep you experience headaches, nasal congestion, or other sinus problems. Rooms in your house have little or no air flow coming from the vents. You're constantly getting sick or are experience more allergies than usual When you turn on the furnace or air conditioner there's musty or stale odor You're experiencing signs of sickness: fatigue, headache, sneezing, stuffy or running nose, irritability, nausea, dry or burning sensation in eyes, nose and throat.[7] 13 Duct (HVAC) Duct sealing Duct Sealing is the sealing of leaks in air ducts in order to reduce air leakage, optimize efficiency, and control entry of pollutants into the home or building. Air pressure combined with air duct leakage can lead to a loss of energy in a HVAC system and duct sealing solves issues of energy loss in the system. Duct tape is not used for sealing ducts. Building codes call for special fire-resistant tapes, often with foil backings and long lasting adhesives. Signs of leaky or poorly performing air ducts include: • Utility bills in winter and summer months above average relative to rate fluctuation • Spaces or rooms that are difficult to heat or cool • Duct location in an attic, attached garage, leaky floor cavity, crawl space or unheated basement.[8] References [1] The Fundamentals volume of the ASHRAE Handbook, ASHRAE, Inc., Atlanta, GA, USA, 2005 [2] HVAC Systems -- Duct Design, 3rd Ed., SMACNA, 1990 [3] "Factory-Made Air Ducts and Air Connectors UL 181" (http:/ / ulstandardsinfonet. ul. com/ scopes/ scopes. asp?fn=0181. html), UL Standards, retrieved September 2, 2009 [4] Designer's Guide to Ceiling-Based Room Air Diffusion, Rock and Zhu, ASHRAE, Inc., Atlanta, GA, USA, 2002 [5] "Should You Have the Air Ducts in Your Home Cleaned?" (http:/ / www. epa. gov/ iaq/ pubs/ airduct. html), U.S. Environmental Protection Agency, retrieved April 17, 2008 [6] "Should You Get Your Heating Ducts Cleaned?" (http:/ / www. cmhc-schl. gc. ca/ en/ co/ maho/ gemare/ gemare_011. cfm), Canadian Mortgage and Housing Corporation, retrieved April 17, 2008 [7] Air Conditioning Explained (http:/ / airconditioningexplained. com/ ?p=15), retrieved 27 July 2009 [8] (http:/ / www. energystar. gov/ index. cfm?c=home_improvement. hm_improvement_ducts) Further reading • Air Diffusion Council Flexible Duct Performance and Installation Standard, 4th Ed., 2003 14 Ear 15 Ear Ear Human (external) ear The ear is the anatomical organ that detects sound. It not only acts as a receiver for sound, but also plays a major role in the sense of balance and body position. The ear is part of the auditory system. The word "ear" may be used correctly to describe the entire organ or just the visible portion. In most mammals, the visible ear is a flap of tissue that is also called the pinna and is the first of many steps in hearing. In people, the pinna is often called the auricle. Vertebrates have a pair of ears, placed symmetrically on opposite sides of the head. This arrangement aids in the ability to localize sound sources. Introduction to ears and hearing Audition is the scientific name for the sense of sound. Sound is a form of energy that moves through air, water, and other matter, in waves of pressure. Sound is the means of auditory communication, including frog calls, bird songs and spoken language. Although the ear is the vertebrate sense organ that recognizes sound, it is the brain and central nervous system that "hears". Sound waves are perceived by the brain through the firing of nerve cells in the auditory portion of the central nervous system. The ear changes sound pressure waves from the outside world into a signal of nerve impulses sent to the brain. The outer part of the ear collects sound. That sound pressure is amplified through the middle portion of the ear and, in land animals, passed from the medium of air into a liquid medium. The change from air to liquid occurs because air surrounds the head and is contained in the ear canal and middle ear, but not in the inner ear. The inner ear is hollow, embedded in the temporal bone, the densest bone of the body. The hollow channels of the inner ear are filled with liquid, and contain a sensory epithelium that is studded with hair cells. The microscopic "hairs" of these cells are structural protein filaments that project out into the fluid. The hair cells are mechanoreceptors that release a chemical neurotransmitter when Anatomy of the human ear. The length of the auditory canal is exaggerated for viewing purposes. stimulated. Sound waves moving through fluid push the filaments; if the filaments bend over enough it causes the hair cells to fire. In this way sound waves are transformed into nerve impulses. In vision, the rods and cones of the Ear 16 retina play a similar role with light as the hair cells do with sound. The nerve impulses travel from the left and right ears through the eighth cranial nerve to both sides of the brain stem and up to the portion of the cerebral cortex dedicated to sound. This auditory part of the cerebral cortex is in the temporal lobe. The part of the ear that is dedicated to sensing balance and position also sends impulses through the eighth cranial nerve, the VIIIth nerve's Vestibular Portion. Those impulses are sent to the vestibular portion of the central nervous system. The human ear can generally hear sounds with frequencies between 20 Hz and 20 kHz (the audio range). Although the sensation of hearing requires an intact and functioning auditory portion of the central nervous system as well as a working ear, human deafness (extreme insensitivity to sound) most commonly occurs because of abnormalities of the inner ear, rather than the nerves or tracts of the central auditory system.[1] Mammalian ear The shape of outer ear of mammals varies widely across species. However the inner workings of mammalian ears (including humans') are very similar. Outer ear (pinna, ear canal, surface of ear drum) The outer ear is the most external portion of the ear. The outer ear includes the pinna (also called auricle), the ear canal, and the very most superficial layer of the ear drum (also called the tympanic membrane). In humans, and almost all vertebrates, the only visible portion of the ear is the outer ear. The word "ear" may properly refer to the pinna (the flesh covered cartilage appendage on either side of the head). This portion of the ear is very vital for hearing. The outer ear does help get sound (and imposes filtering), but the ear canal is very important. Unless the canal is open, hearing will be dampened. Ear wax (cerumen) is produced by glands in the skin of the outer portion of the ear canal. This outer ear canal skin is applied to cartilage; the thinner skin of the deep canal lies on the bone of the Bat pinnae come in different sizes and shapes skull. Only the thicker cerumen-producing ear canal skin has hairs. The outer ear ends at the most superficial layer of the tympanic membrane. The tympanic membrane is commonly called the ear drum. The pinna helps direct sound through the ear canal to the tympanic membrane (eardrum). The framework of the auricle consists of a single piece of yellow fibrocartilage with a complicated relief on the anterior, concave side and a fairly smooth configuration on the posterior, convex side. The Darwinian tubercle, which is present in some people, lies in the descending part of the helix and corresponds to the true ear tip of the long-eared mammals. The lobule merely contains subcutaneous tissue.[2] In some animals with mobile pinnae (like the horse), each pinna can be aimed independently to better receive the sound. For these animals, the pinnae help localize the direction of the sound source. Human beings localize sound within the central nervous system, by comparing arrival-time differences and loudness from each ear, in brain circuits that are connected to both ears. This process is commonly referred to as EPS, or Echo Positioning System. Ear 17 Human outer ear and culture The auricles also have an effect on facial appearance. In Western societies, protruding ears (present in about 5% of ethnic Europeans) have been considered unattractive, particularly if asymmetric. The first surgery to reduce the projection of prominent ears was published in the medical literature in 1881. The ears have also been ornamented with jewelry for thousands of years, traditionally by piercing of the earlobe. In some cultures, ornaments are placed to stretch and enlarge the earlobes. Tearing of the earlobe from the weight of heavy earrings, or from traumatic pull of an earring (for example by snagging on a sweater being removed), is fairly common.[3] The repair of such a tear is usually not difficult. Stretching of the earlobe and various cartilage piercings A cosmetic surgical procedure to reduce the size or change the shape of the ear is called an otoplasty. In the rare cases when no pinna is formed (atresia), or is extremely small (microtia) reconstruction of the auricle is possible. Most often, a cartilage graft from another part of the body (generally, rib cartilage) is used to form the matrix of the ear, and skin grafts or rotation flaps are used to provide the covering skin. Recently ears have been grown on a rat's back and attached to human heads after. However, when babies are born without an auricle on one or both sides, or when the auricle is very tiny, the ear canal is ordinarily either small or absent, and the middle ear often has deformities. The initial medical intervention is aimed at assessing the baby's hearing and the condition of the ear canal, as well as the middle and inner ear. Depending on the results of tests, reconstruction of the outer ear is done in stages, with planning for any possible repairs of the rest of the ear.[4] [5] [6] Middle ear The middle ear, an air-filled cavity behind the ear drum (tympanic membrane), includes the three ear bones or ossicles: the malleus (or hammer), incus (or anvil), and stapes (or stirrup). The opening of the Eustachian tube is also within the middle ear. The malleus has a long process (the manubrium, or handle) that is attached to the mobile portion of the eardrum. The incus is the bridge between the malleus and stapes. The stapes is the smallest named bone in the human body. The three bones are arranged so that movement of the tympanic membrane causes movement of the malleus, which causes movement of the incus, which causes movement of the stapes. When the stapes footplate pushes on the oval window, it causes movement of fluid within the cochlea (a portion of the inner ear). In humans and other land animals the middle ear (like the ear canal) is normally filled with air. Unlike the open ear canal, however, the air of the middle ear is not in direct contact with the atmosphere outside the body. The Eustachian tube connects from the chamber of the middle ear to the back of the nasopharynx. The middle ear is very much like a specialized paranasal sinus, called the tympanic cavity; it, like the paranasal sinuses, is a hollow mucosa-lined cavity in the skull that is ventilated through the nose. The mastoid portion of the human temporal bone, which can be felt as a bump in the skull behind the pinna, also contains air, which is ventilated through the middle ear. Ear 18 Middle Ear Malleus Tensor Tympani Incus Stapedius Labyrinth Stapes Auditory Canal Tympanic Membrane (Ear Drum) Eustachian Tube Tympanic cavity Components of the middle ear Normally, the Eustachian tube is collapsed, but it gapes open both with swallowing and with positive pressure. When taking off in an airplane, the surrounding air pressure goes from higher (on the ground) to lower (in the sky). The air in the middle ear expands as the plane gains altitude, and pushes its way into the back of the nose and mouth. On the way down, the volume of air in the middle ear shrinks, and a slight vacuum is produced. Active opening of the Eustachian tube is required to equalize the pressure between the middle ear and the surrounding atmosphere as the plane descends. The diver also experiences this change in pressure, but with greater rates of pressure change; active opening of the Eustachian tube is required more frequently as the diver goes deeper into higher pressure. The arrangement of the tympanic membrane and ossicles works to efficiently couple the sound from the opening of the ear canal to the cochlea. There are several simple mechanisms that combine to increase the sound pressure. The first is the "hydraulic principle". The surface area of the tympanic membrane is many times that of the stapes footplate. Sound energy strikes the tympanic membrane and is concentrated to the smaller footplate. A second mechanism is the "lever principle". The dimensions of the articulating ear ossicles lead to an increase in the force applied to the stapes footplate compared with that applied to the malleus. A third mechanism channels the sound pressure to one end of the cochlea, and protects the other end from being struck by sound waves. In humans, this is called "round window protection", and will be more fully discussed in the next section. Abnormalities such as impacted ear wax (occlusion of the external ear canal), fixed or missing ossicles, or holes in the tympanic membrane generally produce conductive hearing loss. Conductive hearing loss may also result from middle ear inflammation causing fluid build-up in the normally air-filled space. Tympanoplasty is the general name of the operation to repair the middle ear's tympanic membrane and ossicles. Grafts from muscle fascia are ordinarily used to rebuild an intact ear drum. Sometimes artificial ear bones are placed to substitute for damaged ones, or a disrupted ossicular chain is rebuilt in order to conduct sound effectively. Ear 19 Inner ear: cochlea, vestibule, and semicircular canals Inner Ear Posterior Canal Superior Canal Utricle Horizontal Canal Vestibule Cochlea Saccule Components of the inner ear The inner ear includes both the organ of hearing (the cochlea) and a sense organ that is attuned to the effects of both gravity and motion (labyrinth or vestibular apparatus). The balance portion of the inner ear consists of three semicircular canals and the vestibule. The inner ear is encased in the hardest bone of the body. Within this ivory hard bone, there are fluid-filled hollows. Within the cochlea are three fluid filled spaces: the scala tympani, the scala vestibuli and the scala media. The eighth cranial nerve comes from the brain stem to enter the inner ear. When sound strikes the ear drum, the movement is transferred to the footplate of the stapes, which presses it into one of its fluid-filled ducts through the oval window of cochlea . The fluid inside this duct is moved, flowing against the receptor cells of the Organ of Corti, which fire. These stimulate the spiral ganglion, which sends information through the auditory portion of the eighth cranial nerve to the brain. Hair cells are also the receptor cells involved in balance, although the hair cells of the auditory and vestibular systems of the ear are not identical. Vestibular hair cells are stimulated by movement of fluid in the semicircular canals and the utricle and saccule. Firing of vestibular hair cells stimulates the Vestibular portion of the eighth cranial nerve.[7] Damage to the human ear Outer ear trauma Auricle The auricle can be easily damaged. Because it is skin-covered cartilage, with only a thin padding of connective tissue, rough handling of the ear can cause enough swelling to jeopardize the blood-supply to its framework, the auricular cartilage. That entire cartilage framework is fed by a thin covering membrane called the perichondrium (meaning literally: around the cartilage). Any fluid from swelling or blood from injury that collects between the perichondrium and the underlying cartilage puts the cartilage in danger of being separated from its supply of nutrients. If portions of the cartilage starve and die, the ear never heals back into its normal shape. Instead, the cartilage becomes lumpy and distorted. Wrestler's Ear is one term used to describe the result, because wrestling is one of the most common ways such an injury occurs. Cauliflower ear is another name for the same condition, Ear 20 because the thickened auricle can resemble that vegetable. The lobule of the ear (ear lobe) is the one part of the human auricle that normally contains no cartilage. Instead, it is a wedge of adipose tissue (fat) covered by skin. There are many normal variations to the shape of the ear lobe, which may be small or large. Tears of the earlobe can be generally repaired with good results. Since there is no cartilage, there is not the risk of deformity from a blood clot or pressure injury to the ear lobe. Other injuries to the external ear occur fairly frequently, and can leave a major deformity. Some of the more common ones include, laceration from glass, knives, and bite injuries, avulsion injuries, cancer, frostbite, and burns. Ear canal Ear canal injuries can come from firecrackers and other explosives, and mechanical trauma from placement of foreign bodies into the ear. The ear canal is most often self-traumatized from efforts at ear cleaning. The outer part of the ear canal rests on the flesh of the head; the inner part rests in the opening of the bony skull (called the external auditory meatus). The skin is very different on each part. The outer skin is thick, and contains glands as well as hair follicles. The glands make cerumen (also called ear wax). The skin of the outer part moves a bit if the pinna is pulled; it is only loosely applied to the underlying tissues. The skin of the bony canal, on the other hand, is not only among the most delicate skin in the human body, it is tightly applied to the underlying bone. A slender object used to blindly clean cerumen out of the ear often results instead with the wax being pushed in, and contact with the thin skin of the bony canal is likely to lead to laceration and bleeding. Middle ear trauma Like outer ear trauma, middle ear trauma most often comes from blast injuries and insertion of foreign objects into the ear. Skull fractures that go through the part of the skull containing the ear structures (the temporal bone) can also cause damage to the middle ear. Small perforations of the tympanic membrane usually heal on their own, but large perforations may require grafting. Displacement of the ossicles will cause a conductive hearing loss that can only be corrected with surgery. Forcible displacement of the stapes into the inner ear can cause a sensory neural hearing loss that cannot be corrected even if the ossicles are put back into proper position. Because human skin has a top waterproof layer of dead skin cells that are constantly shedding, displacement of portions of the tympanic membrane or ear canal into the middle ear or deeper areas by trauma can be particularly traumatic. If the displaced skin lives within a closed area, the shed surface builds up over months and years and forms a cholesteatoma. The -oma ending of that word indicates a tumour in medical terminology, and although cholesteatoma is not a neoplasm (but a skin cyst), it can expand and erode the ear structures. The treatment for cholesteatoma is surgical. Inner ear trauma There are two principal damage mechanisms to the inner ear in industrialized society, and both injure hair cells. The first is exposure to elevated sound levels (noise trauma), and the second is exposure to drugs and other substances (ototoxicity). In 1972 the U.S. EPA told Congress that at least 34 million people were exposed to sound levels on a daily basis that are likely to lead to significant hearing loss.[8] The worldwide implication for industrialized countries would place this exposed population in the hundreds of millions. The National Institute for Occupational Safety and Health has recently published research on the estimated numbers of persons with hearing difficulty (11%) and the percentage that can be attributed to occupational noise exposure (24%).[9] Furthermore, according to the National Health and Nutrition Examination Survey (NHANES), approximately twenty-two million (17%) US workers reported exposure to hazardous workplace noise.[10] Workers exposed to hazardous noise further exacerbate the potential for developing noise induced hearing loss when they do not wear (hearing protection). Ear 21 Vestigial structures It has long been known that humans, and indeed primates such as the orangutan and chimpanzee have ear muscles that are minimally developed and non-functional, yet still large enough to be easily identifiable.[11] These undeveloped muscles are vestigial structures. A muscle that cannot move the ear, for whatever reason, can no longer be said to have any biological function. This serves as evidence of homology between related species. In humans there is variability in these muscles, such that some people are able to move their ears in various directions, and it has been said that it may be possible for others to gain such movement by repeated trials.[11] In such primates the inability to move the ear is compensated mainly by the ability to turn the head on a horizontal plane, an ability which is not common to most monkeys—a function once provided by one structure is now replaced by another.[12] Comparative anatomy of primate ears: Human (left) and Barbary Macaque (right). The outer structure of the ear also shows some vestigial features, such as the node or point on the helix of the ear known as Darwin's tubercle which is found in around 10% of the population, this feature is labelled (a) in the accompanying figure. Invertebrate hearing organs Only vertebrate animals have ears, although many invertebrates are able to detect sound using other kinds of sense organs. In insects, tympanal organs are used to hear distant sounds. They are not confined to the head, but can occur in different locations depending on the group of insects.[13] Human ear (from Descent of Man) The tympanal organs of some insects are extremely sensitive, offering acute hearing beyond that of most other animals. The female cricket fly Ormia ochracea has a tympanal organs on each side of her abdomen. They are connected by a thin bridge of exoskeleton and they function like a tiny pair of ear drums, but because they are linked, they provide acute directional information. The fly uses her "ears" to detect the call of her host, a male cricket. Depending on where the song of the cricket is coming from the fly's hearing organs will reverberate at slightly different frequencies. This difference may be as little as 50 billionths of a second, but it is enough to allow the fly to home in directly on a singing male cricket and parasitize it.[14] Simpler structures allow arthropods to detect near field sounds. Spiders and cockroaches, for example, have hairs on their legs which are used for detecting sound. Caterpillars may also have hairs on their body that perceive vibrations[15] and allow them to respond to the sound. Ear 22 References [1] Greinwald, John H. Jr MD; Hartnick, Christopher J. MD The Evaluation of Children With Hearing Loss. Archives of Otolaryngology — Head & Neck Surgery. 128(1):84-87, January 2002 [2] Stenström, J. Sten: Deformities of the ear; In: Grabb, W., C., Smith, J.S. (Edited): “Plastic Surgery”, Little, Brown and Company, Boston, 1979, ISBN 0-316-32269-5 (C), ISBN 0-316-32268-7 (P) [3] Deborah S. Sarnoff, Robert H. Gotkin, and Joan Swirsky (2002). Instant Beauty: Getting Gorgeous on Your Lunch Break (http:/ / books. google. com/ books?id=ljeY_Tvyl_MC& pg=PA60& ots=pt_I8xjg9k& dq=earlobe+ tear+ earring& sig=YBnRJSoIUiA1Kjhrzpq_Odd_0yk). St. Martin's Press. ISBN 031228697X. . [4] Lam SM. Edward Talbot Ely: father of aesthetic otoplasty. [Biography. Historical Article. Journal Article] Archives of Facial Plastic Surgery. 6(1):64, 2004 Jan-Feb. [5] Siegert R. Combined reconstruction of congenital auricular atresia and severe microtia. [Evaluation Studies. Journal Article] Laryngoscope. 113(11):2021-7; discussion 2028-9, 2003 Nov. [6] Trigg DJ. Applebaum EL. Indications for the surgical repair of unilateral aural atresia in children. [Review] [33 refs] [Journal Article. Review], American Journal of Otology. 19(5):679-84; discussion 684-6, 1998 September [7] Anson and Donaldson, Surgical Anatomy of the Temporal Bone, 4th Edition, Raven Press, 1992 [8] Senate Public Works Committee, Noise Pollution and Abatement Act of 1972, S. Rep. No. 1160, 92nd Cong. 2nd session. [9] Tak SW, Calvert GM, "Hearing Difficulty Attributable to Employment by Industry and Occupation: An Analysis of the National Health Interview Survey - United States, 1997 to 2003," J. Occup. Env. Med. 2008, 50:46-56 [10] Tak SW, Davis RR, Calvert GM "Exposure to Hazardous Workplace Noise and Use of Hearing Protection Devices Among US WOrkers, 1999-2004," Am. J. Ind. Med. 2009, 52:358-371 [11] Darwin, Charles (1871). The Descent of Man, and Selection in Relation to Sex. John Murray: London. [12] Mr. St. George Mivart, Elementary Anatomy, 1873, p. 396. [13] Yack, JE, and JH Fullard, 1993. What is an insect ear? Ann. Entomol. Soc. Am. 86(6): 677-682. [14] Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press. [15] Scoble, MJ. 1992. The Lepidoptera: Form, function, and diversity. Oxford University Press. External links • • • • • Protein behind hearing (http://news.bbc.co.uk/2/hi/health/3740680.stm) 3D Ear page (http://audilab.bmed.mcgill.ca/~daren/3Dear/3d_ear_homepage.html) Details of various ear problems (http://www.entusa.com/external_ear_canal.htm) Ear wiggling mechanism unmasked (http://www.abc.net.au/science/articles/2006/05/25/1647353.htm) Cotton swabs can pose serious health risk: coroner from ctv.ca (http://www.ctv.ca/servlet/ArticleNews/story/ CTVNews/20080205/cotton_swab_080205/20080205?hub=Health) • Radiology of the Ear Canal (http://rad.usuhs.edu/medpix/master.php3?mode=case_viewer&pt_id=13048& imid=49500&quiz=no#top) from MedPix Eye 23 Eye Eye Schematic diagram of the vertebrate eye. Compound eye of Antarctic krill Eyes are organs that detect light, and convert it to electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment; regulates its intensity through a diaphragm; focuses it through an adjustable assembly of lenses to form an image; converts this image into a set of electrical signals; and transmits these signals to the brain, through complex neural pathways that connect the eye, via the optic nerve, to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system.[1] Image-resolving eyes are present in molluscs, chordates and arthropods.[2] The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian Eye 24 adjustment. Overview Complex eyes can distinguish shapes and colours. The visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception; in other organisms, eyes are located so as to maximize the field of view, such as in rabbits and horses, which have monocular vision. According to the theory of biological evolution, the first proto-eyes evolved among animals 600 million years ago, about the time of the Cambrian explosion.[3] The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in six of the thirty-plus[4] main phyla.[1] In most vertebrates and some molluscs, the Eye of the wisent, the European bison eye works by allowing light to enter and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells (for colour) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals for vision. The visual signals are then transmitted to the brain via the optic nerve. Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often an iris; the relaxing or tightening of the muscles around the iris change the size of the pupil, thereby regulating the amount of light that enters the eye,[5] and reducing aberrations when there is enough light.[6] The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing vision is achieved [7] by telescoping the lens—similar to how a camera focuses. Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors, which are arranged hexagonally, and which can give a full 360-degree field of vision. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have compound eyes of only a few facets, each with a retina capable of creating an image, creating vision. With each eye viewing a different thing, a fused image from all the eyes is produced in the brain, providing very different, high-resolution images. Possessing detailed hyperspectral colour vision, the Mantis shrimp has been reported to have the world's most complex colour vision system.[8] Trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods, which have soft eyes. The number of lenses in such an eye varied, however: some trilobites had only one, and some had thousands of lenses in one eye. In contrast to compound eyes, simple eyes are those that have a single lens. For example, jumping spiders have a large pair of simple eyes with a narrow field of view, supported by an array of other, smaller eyes for peripheral vision. Some insect larvae, like caterpillars, have a different type of simple eye (stemmata) which gives a rough image. Some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot actually "see" in the normal sense. They do have photosensitive cells, but no lens and no other means of projecting an image onto these cells. They can distinguish between light and dark, but no more. This enables snails to keep out of direct sunlight. In organisms dwelling near deep-sea vents, compound eyes have been secondarily simplified and adapted to spot the infra-red light produced by the hot vents–in this way the bearers can spot hot springs and avoid Eye 25 being boiled alive.[9] Evolution Photoreception is phylogenetically very old, with various theories of phylogenesis.[10] The common origin (monophyly) of all animal eyes is now widely accepted as fact. This is based upon the shared anatomical and genetic features of all eyes; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 540 million years ago.[11] [12] [13] The majority of the advancements in early eyes are believed to have taken only a few million years to develop, since the first predator to gain true imaging would have touched off an "arms race".[14] Prey animals and competing predators alike would be at a distinct disadvantage without such capabilities and would be less likely to survive and reproduce. Hence multiple eye types and subtypes developed in parallel. Eyes in various animals show adaption to their requirements. For example, birds of prey have much greater visual acuity than humans, and some can see ultraviolet light. The different forms of eye in, for example, vertebrates and mollusks are often cited as examples of parallel evolution, despite their distant common ancestry. Evolution of the eye The very earliest "eyes", called eyespots, were simple patches of photoreceptor protein in unicellular animals. In multicellular beings, multicellular eyespots evolved, physically similar to the receptor patches for taste and smell. These eyespots could only sense ambient brightness: they could distinguish light and dark, but not the direction of the lightsource.[15] Through gradual change, as the eyespot depressed into a shallow "cup" shape, the ability to slightly discriminate directional brightness was achieved by using the angle at which the light hit certain cells to identify the source. The pit deepened over time, the opening diminished in size, and the number of photoreceptor cells increased, forming an effective pinhole camera that was capable of dimly distinguishing shapes.[16] The thin overgrowth of transparent cells over the eye's aperture, originally formed to prevent damage to the eyespot, allowed the segregated contents of the eye chamber to specialize into a transparent humour that optimized color filtering, blocked harmful radiation, improved the eye's refractive index, and allowed functionality outside of water. The transparent protective cells eventually split into two layers, with circulatory fluid in between that allowed wider viewing angles and greater imaging resolution, and the thickness of the transparent layer gradually increased, in most species with the transparent crystallin protein.[17] The gap between tissue layers naturally formed a bioconvex shape, an optimally ideal structure for a normal refractive index. Independently, a transparent layer and a nontransparent layer split forward from the lens: the cornea and iris. Separation of the forward layer again formed a humour, the aqueous humour. This increased refractive power and again eased circulatory problems. Formation of a nontransparent ring allowed more blood vessels, more circulation, and larger eye sizes.[17] Eye 26 Types of eye There are ten different eye layouts—indeed every way of capturing an optical image commonly used by man, with the exceptions of zoom and Fresnel lenses. Eye types can be categorized into "simple eyes", with one concave photoreceptive surface, and "compound eyes", which comprise a number of individual lenses laid out on a convex surface.[1] Note that "simple" does not imply a reduced level of complexity or acuity. Indeed, any eye type can be adapted for almost any behaviour or environment. The only limitations specific to eye types are that of resolution—the physics of compound eyes prevents them from achieving a resolution better than 1°. Also, superposition eyes can achieve greater sensitivity than apposition eyes, so are better suited to dark-dwelling creatures.[1] Eyes also fall into two groups on the basis of their photoreceptor's cellular construction, with the photoreceptor cells either being cilliated (as in the vertebrates) or rhabdomeric. These two groups are not monophyletic; the cnidaria also possess cilliated cells, [18] and some annelids possess both.[19] Non-compound eyes Simple eyes are rather ubiquitous, and lens-bearing eyes have evolved at least seven times in vertebrates, cephalopods, annelids, crustacea and cubozoa.[20] Pit eyes Pit eyes, also known as stemma, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eyespot, to allow the organism to deduce the angle of incoming light.[1] Found in about 85% of phyla, these basic forms were probably the precursors to more advanced types of "simple eye". They are small, comprising up to about 100 cells covering about 100 µm.[1] The directionality can be improved by reducing the size of the aperture, by incorporating a reflective layer behind the receptor cells, or by filling the pit with a refractile material.[1] Pit vipers have developed pits that function as eyes by sensing thermal infra-red radiation, in addition to their optical wavelength eyes like those of other vertebrates. Spherical lensed eye The resolution of pit eyes can be greatly improved by incorporating a material with a higher refractive index to form a lens, which may greatly reduce the blur radius encountered—hence increasing the resolution obtainable.[1] The most basic form, seen in some gastropods and annelids, consists of a lens of one refractive index. A far sharper image can be obtained using materials with a high refractive index, decreasing to the edges; this decreases the focal length and thus allows a sharp image to form on the retina.[1] This also allows a larger aperture for a given sharpness of image, allowing more light to enter the lens; and a flatter lens, reducing spherical aberration.[1] Such an inhomogeneous lens is necessary in order for the focal length to drop from about 4 times the lens radius, to 2.5 radii.[1] Heterogeneous eyes have evolved at least eight times: four or more times in gastropods, once in the copepods, once in the annelids and once in the cephalopods.[1] No aquatic organisms possess homogeneous lenses; presumably the evolutionary pressure for a heterogeneous lens is great enough for this stage to be quickly "outgrown".[1] This eye creates an image that is sharp enough that motion of the eye can cause significant blurring. To minimize the effect of eye motion while the animal moves, most such eyes have stabilizing eye muscles.[1] The ocelli of insects bear a simple lens, but their focal point always lies behind the retina; consequently they can never form a sharp image. This capitulates the function of the eye. Ocelli (pit-type eyes of arthropods) blur the image across the whole retina, and are consequently excellent at responding to rapid changes in light intensity across the whole visual field; this fast response is further accelerated by the large nerve bundles which rush the information to the brain.[21] Focusing the image would also cause the sun's image to be focused on a few receptors, with the possibility of damage under the intense light; shielding the receptors would block out some light and thus reduce their sensitivity.[21] This fast response has led to suggestions that the ocelli of insects are used mainly in flight, Eye 27 because they can be used to detect sudden changes in which way is up (because light, especially UV light which is absorbed by vegetation, usually comes from above).[21] Multiple lenses Some marine organisms bear more than one lens; for instance the copepod Pontella has three. The outer has a parabolic surface, countering the effects of spherical aberration while allowing a sharp image to be formed. Another copepod, Copilia's eyes have two lenses, arranged like those in a telescope.[1] Such arrangements are rare and poorly understood, but represent an interesting alternative construction. An interesting use of multiple lenses is seen in some hunters such as eagles and jumping spiders, which have a refractive cornea (discussed next): these have a negative lens, enlarging the observed image by up to 50% over the receptor cells, thus increasing their optical resolution.[1] Refractive cornea In the eyes of most mammals, birds, reptiles, and most other terrestrial vertebrates (along with spiders and some insect larvae) the vitreous fluid has a higher refractive index than the air.[1] In general, the lens is not spherical. Spherical lenses produce spherical aberration. In refractive corneas, the lens tissue is corrected with inhomogeneous lens material (See Luneburg lens.), or with an aspheric shape.[1] Flattening the lens has a disadvantage; the quality of vision is diminished away from the main line of focus. Thus, animals that have evolved with a wide field-of-view often have eyes that make use of an inhomogeneous lens.[1] As mentioned above, a refractive cornea is only useful out of water; in water, there is little difference in refractive index between the vitreous fluid and the surrounding water. Hence creatures that have returned to the water—--penguins and seals, for example---lose their highly curved cornea and return to lens-based vision. An alternative solution, borne by some divers, is to have a very strongly focusing cornea.[1] Reflector eyes An alternative to a lens is to line the inside of the eye with " mirrors", and reflect the image to focus at a central point.[1] The nature of these eyes means that if one were to peer into the pupil of an eye, one would see the same image that the organism would see, reflected back out.[1] Many small organisms such as rotifers, copeopods and platyhelminths use such organs, but these are too small to produce usable images.[1] Some larger organisms, such as scallops, also use reflector eyes. The scallop Pecten has up to 100 millimeter-scale reflector eyes fringing the edge of its shell. It detects moving objects as they pass successive lenses.[1] There is at least one vertebrate, the spookfish, whose eyes include reflective optics for focusing of light. Each of the two eyes of a spookfish collects light from both above and below; the light coming from above is focused by a lens, while that coming from below, by a curved mirror composed of many layers of small reflective plates made of guanine crystals.[22] Eye 28 Compound eyes A compound eye may consist of thousands of individual photoreceptor units or ommatidia (ommatidium, singular). The image perceived is a combination of inputs from the numerous ommatidia (individual "eye units"), which are located on a convex surface, thus pointing in slightly different directions. Compared with simple eyes, compound eyes possess a very large view angle, and can detect fast movement and, in some cases, the polarization of light.[23] Because the individual lenses are so small, the effects of diffraction impose a limit on the possible resolution that can be obtained (assuming that they do not function as phased arrays). This can only be countered by increasing lens size and number. To see with a resolution comparable to our simple eyes, humans would require compound eyes which would each reach the size of their head. An image of a house fly compound eye surface by using Scanning Electron Microscope Compound eyes fall into two groups: apposition eyes, which form multiple inverted images, and superposition eyes, which form a single erect image.[24] Compound eyes are common in arthropods, and are also present in annelids and some bivalved molluscs.[25] Compound eyes, in arthropods at least, grow at their margins by [26] the addition of new ommatidia. Anatomy of the compound eye of an insect Arthropods such as this Calliphora vomitoria fly have compound eyes Eye 29 Apposition eyes Apposition eyes are the most common form of eye, and are presumably the ancestral form of compound eye. They are found in all arthropod groups, although they may have evolved more than once within this phylum.[1] Some annelids and bivalves also have apposition eyes. They are also possessed by Limulus, the horseshoe crab, and there are suggestions that other chelicerates developed their simple eyes by reduction from a compound starting point.[1] (Some caterpillars appear to have evolved compound eyes from simple eyes in the opposite fashion.) Apposition eyes work by gathering a number of images, one from each eye, and combining them in the brain, with each eye typically contributing a single point of information. Structure of the ommatidia of apposition compound eyes The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. In the other kind of apposition eye, found in the Strepsiptera, lenses are not fused to one another, and each forms an entire image; these images are combined in the brain. This is called the schizochroal compound eye or the neural superposition eye. Because images are combined additively, this arrangement allows vision under lower light levels.[1] Superposition eyes The second type is named the superposition eye. The superposition eye is divided into three types; the refracting, the reflecting and the parabolic superposition eye. The refracting superposition eye has a gap between the lens and the rhabdom, and no side wall. Each lens takes light at an angle to its axis and reflects it to the same angle on the other side. The result is an image at half the radius of the eye, which is where the tips of the rhabdoms are. This kind is used mostly by nocturnal insects. In the parabolic superposition compound eye type, seen in arthropods such as mayflies, the parabolic surfaces of the inside of each facet focus light from a reflector to a sensor array. Long-bodied decapod crustaceans such as shrimp, prawns, crayfish and lobsters are alone in having reflecting superposition eyes, which also have a transparent gap but use corner mirrors instead of lenses. Parabolic superposition This eye type functions by refracting light, then using a parabolic mirror to focus the image; it combines features of [9] superposition and apposition eyes. Other Good fliers like flies or honey bees, or prey-catching insects like praying mantis or dragonflies, have specialized zones of ommatidia organized into a fovea area which gives acute vision. In the acute zone the eyes are flattened and the facets larger. The flattening allows more ommatidia to receive light from a spot and therefore higher resolution. There are some exceptions from the types mentioned above. Some insects have a so-called single lens compound eye, a transitional type which is something between a superposition type of the multi-lens compound eye and the single lens eye found in animals with simple eyes. Then there is the mysid shrimp Dioptromysis paucispinosa. The shrimp has an eye of the refracting superposition type, in the rear behind this in each eye there is a single large facet that is three times in diameter the others in the eye and behind this is an enlarged crystalline cone. This projects an Eye 30 upright image on a specialized retina. The resulting eye is a mixture of a simple eye within a compound eye. Another version is the pseudofaceted eye, as seen in Scutigera. This type of eye consists of a cluster of numerous ocelli on each side of the head, organized in a way that resembles a true compound eye. The body of Ophiocoma wendtii, a type of brittle star, is covered with ommatidia, turning its whole skin into a compound eye. The same is true of many chitons. The tube feet of sea urchins contain photoreceptor proteins, which together act as a compound eye; they lack screening pigments, but can detect the directionality of light by the shadow cast by its opaque body.[27] Nutrients of the eye The ciliary body is triangular in horizontal section and is coated by a double layer, the ciliary epithelium. The inner layer is transparent and covers the vitreous body, and is continuous from the neural tissue of the retina. The outer layer is highly pigmented, continuous with the retinal pigment epithelium, and constitutes the cells of the dilator muscle. The vitreous is the transparent, colorless, gelatinous mass that fills the space between the lens of the eye and the retina lining the back of the eye.[28] It is produced by certain retinal cells. It is of rather similar composition to the cornea, but contains very few cells (mostly phagocytes which remove unwanted cellular debris in the visual field, as well as the hyalocytes of Balazs of the surface of the vitreous, which reprocess the hyaluronic acid), no blood vessels, and 98-99% of its volume is water (as opposed to 75% in the cornea) with salts, sugars, vitrosin (a type of collagen), a network of collagen type II fibers with the mucopolysaccharide hyaluronic acid, and also a wide array of proteins in micro amounts. Amazingly, with so little solid matter, it tautly holds the eye. Relationship to life requirements Eyes are generally adapted to the environment and life requirements of the organism which bears them. For instance, the distribution of photoreceptors tends to match the area in which the highest acuity is required, with horizon-scanning organisms, such as those that live on the African plains, having a horizontal line of high-density ganglia, while tree-dwelling creatures which require good all-round vision tend to have a symmetrical distribution of ganglia, with acuity decreasing outwards from the centre. Of course, for most eye types, it is impossible to diverge from a spherical form, so only the density of optical receptors can be altered. In organisms with compound eyes, it is the number of ommatidia rather than ganglia that reflects the region of highest data acquisition.[1] :23-4 Optical superposition eyes are constrained to a spherical shape, but other forms of compound eyes may deform to a shape where more ommatidia are aligned to, say, the horizon, without altering the size or density of individual ommatidia.[29] Eyes of horizon-scanning organisms have stalks so they can be easily aligned to the horizon when this is inclined, for example if the animal is on a slope.[30] An extension of this concept is that the eyes of predators typically have a zone of very acute vision at their centre, to assist in the identification of prey.[29] In deep water organisms, it may not be the centre of the eye that is enlarged. The hyperiid amphipods are deep water animals that feed on organisms above them. Their eyes are almost divided into two, with the upper region thought to be involved in detecting the silhouettes of potential prey—or predators—against the faint light of the sky above. Accordingly, deeper water hyperiids, where the light against which the silhouettes must be compared is dimmer, have larger "upper-eyes", and may lose the lower portion of their eyes altogether.[29] Depth perception can be enhanced by having eyes which are enlarged in one direction; distorting the eye slightly allows the distance to the object to be estimated with a high degree of accuracy.[9] Acuity is higher among male organisms that mate in mid-air, as they need to be able to spot and assess potential mates against a very large backdrop.[29] On the other hand, the eyes of organisms which operate in low light levels, such as around dawn and dusk or in deep water, tend to be larger to increase the amount of light that can be captured.[29] Eye 31 It is not only the shape of the eye that may be affected by lifestyle. Eyes can be the most visible parts of organisms, and this can act as a pressure on organisms to have more transparent eyes at the cost of function.[29] Eyes may be mounted on stalks to provide better all-round vision, by lifting them above an organism's carapace; this also allows them to track predators or prey without moving the head.[9] Visual acuity Visual acuity, or resolving power, is "the ability to distinguish fine detail" and is the property of cones.[28] It is often measured in cycles per degree (CPD), which measures an angular resolution, or how much an eye can differentiate one object from another in terms of visual angles. Resolution in CPD can be measured by bar charts of different numbers of white/black stripe cycles. For example, if each pattern is 1.75 cm wide and is placed at 1 m distance from the eye, it will subtend an angle of 1 degree, so the number of white/black bar pairs on the pattern will be a measure of the cycles per degree of that pattern. The highest such number that the eye can resolve as stripes, or distinguish from a gray block, is then the measurement of visual acuity of the eye. A hawk's eye For a human eye with excellent acuity, the maximum theoretical resolution is 50 CPD[31] (1.2 arcminute per line pair, or a 0.35 mm line pair, at 1 m). A rat can resolve only about 1 to 2 CPD.[32] A horse has higher acuity through most of the visual field of its eyes than a human has, but does not match the high acuity of the human eye's central fovea region. Spherical aberration limits the resolution of a 7 mm pupil to about 3 arcminutes per line pair. At a pupil diameter of 3 mm, the spherical aberration is greatly reduced, resulting in an improved resolution of approximately 1.7 arcminutes per line pair.[33] A resolution of 2 arcminutes per line pair, equivalent to a 1 arcminute gap in an optotype, corresponds to 20/20 (normal vision) in humans. Perception of colours "Colour vision is the faculty of the organism to distinguish lights of different spectral qualities."[28] All organisms are restricted to a small range of electromagnetic spectrum; this varies from creature to creature, but is mainly between wavelengths of 400 and 700 nm.[34] This is a rather small section of the electromagnetic spectrum, probably reflecting the submarine evolution of the organ: water blocks out all but two small windows of the EM spectrum, and there has been no evolutionary pressure among land animals to broaden this range.[35] The most sensitive pigment, rhodopsin, has a peak response at 500 nm.[36] Small changes to the genes coding for this protein can tweak the peak response by a few nm;[2] pigments in the lens can also filter incoming light, changing the peak response.[2] Many organisms are unable to discriminate between colours, seeing instead in shades of grey; colour vision necessitates a range of pigment cells which are primarily sensitive to smaller ranges of the spectrum. In primates, geckos, and other organisms, these take the form of cone cells, from which the more sensitive rod cells evolved.[36] Even if organisms are physically capable of discriminating different colours, this does not necessarily mean that they can perceive the different colours; only with behavioural tests can this be deduced.[2] Most organisms with colour vision are able to detect ultraviolet light. This high energy light can be damaging to receptor cells. With a few exceptions (snakes, placental mammals), most organisms avoid these effects by having absorbent oil droplets around their cone cells. The alternative, developed by organisms that had lost these oil droplets in the course of evolution, is to make the lens impervious to UV light — this precludes the possibility of any UV light being detected, as it does not even reach the retina.[36] Eye 32 Rods and cones The retina contains two major types of light-sensitive photoreceptor cells used for vision: the rods and the cones. Rods cannot distinguish colours, but are responsible for low-light (scotopic) monochrome (black-and-white) vision; they work well in dim light as they contain a pigment, rhodopsin (visual purple), which is sensitive at low light intensity, but saturates at higher (photopic) intensities. Rods are distributed throughout the retina but there are none at the fovea and none at the blind spot. Rod density is greater in the peripheral retina than in the central retina. Cones are responsible for colour vision. They require brighter light to function than rods require. In humans, there are three types of cones, maximally sensitive to long-wavelength, medium-wavelength, and short-wavelength light (often referred to as red, green, and blue, respectively, though the sensitivity peaks are not actually at these colours). The colour seen is the combined effect of stimuli to, and responses from, these three types of cone cells. Cones are mostly concentrated in and near the fovea. Only a few are present at the sides of the retina. Objects are seen most sharply in focus when their images fall on the fovea, as when one looks at an object directly. Cone cells and rods are connected through intermediate cells in the retina to nerve fibres of the optic nerve. When rods and cones are stimulated by light, the nerves send off impulses through these fibres to the brain.[36] Pigmentation The pigment molecules used in the eye are various, but can be used to define the evolutionary distance between different groups, and can also be an aid in determining which are closely related – although problems of convergence do exist.[36] Opsins are the pigments involved in photoreception. Other pigments, such as melanin, are used to shield the photoreceptor cells from light leaking in from the sides. The opsin protein group evolved long before the last common ancestor of animals, and has continued to diversify since.[2] There are two types of opsin involved in vision; c-opsins, which are associated with ciliary-type photoreceptor cells, and r-opsins, associated with rhabdomeric photoreceptor cells.[37] The eyes of vertebrates usually contain cilliary cells with c-opsins, and (bilaterian) invertebrates have rhabdomeric cells in the eye with r-opsins. However, some ganglion cells of vertebrates express r-opsins, suggesting that their ancestors used this pigment in vision, and that remnants survive in the eyes.[37] Likewise, c-opsins have been found to be expressed in the brain of some invertebrates. They may have been expressed in ciliary cells of larval eyes, which were subsequently resorbed into the brain on metamorphosis to the adult form.[37] C-opsins are also found in some derived bilaterian-invertebrate eyes, such as the pallial eyes of the bivalve molluscs; however, the lateral eyes (which were presumably the ancestral type for this group, if eyes evolved once there) always use r-opsins.[37] Cnidaria, which are an outgroup to the taxa mentioned above, express c-opsins - but r-opsins are yet to be found in this group.[37] Incidentally, the melanin produced in the raticate is produced in the same fashion as that in vertebrates, suggesting the common descent of this pigment.[37] Eye 33 References Notes [1] Land, M F; Fernald, R D (1992). "The Evolution of Eyes". Annual Review of Neuroscience 15: 1–29. doi:10.1146/annurev.ne.15.030192.000245. PMID 1575438. [2] Frentiu, Francesca D.; Adriana D. Briscoe (2008). "A butterfly eye's view of birds". BioEssays 30 (11-12): 1151–62. doi:10.1002/bies.20828. PMID 18937365. [3] Breitmeyer, Bruno (2010). Blindspots: The Many Ways We Cannot See. New York: Oxford University Press. p. 4. ISBN 9780195394269. [4] The precise number depends on the author [5] Nairne, James (2005). Psychology (http:/ / books. google. com/ ?id=6MqkLT-Q0oUC& pg=PA146& dq=iris+ intitle:psychology+ inauthor:Nairne). Belmont: Wadsworth Publishing. ISBN 049503150x. OCLC 61361417. . [6] Vicki Bruce, Patrick R. Green, and Mark A. Georgeson (1996). Visual Perception: Physiology, Psychology and Ecology (http:/ / books. google. com/ ?id=ukvei0wge_8C& pg=PA20& dq=iris+ aberrations+ intitle:psychology). Psychology Press. pp. 20. ISBN 0863774504. . [7] BioMedia Associates Educational Biology Site: What animal has a more sophisticated eye, Octopus or Insect? (http:/ / ebiomedia. com/ gall/ eyes/ octopus-insect. html) [8] Who You Callin' "Shrimp"? – National Wildlife Magazine (http:/ / www. nwf. org/ nationalwildlife/ article. cfm?issueID=77& articleID=1114) [9] doi: 10.1007/s12052-008-0085-0 This citation will be automatically completed in the next few minutes. You can jump the queue or expand by hand (http:/ / en. wikipedia. org/ wiki/ Template:cite_doi/ _10. 1007. 2fs12052-008-0085-0_?preload=Template:Cite_doi/ preload& editintro=Template:Cite_doi/ editintro& action=edit) [10] Autrum, H. "Introduction". In H. Autrum (editor). Comparative Physiology and Evolution of Vision in Invertebrates- A: Invertebrate Photoreceptors. Handbook of Sensory Physiology. VII/6A. New York: Springer-Verlag. pp. 4, 8–9. ISBN 3540088377 [11] Halder, G.; Callaerts, P.; Gehring, W.J. (1995). "New perspectives on eye evolution". Curr. Opin. Genet. Dev. 5 (5): 602–609. doi:10.1016/0959-437X(95)80029-8. PMID 8664548. [12] Halder, G.; Callaerts, P.; Gehring, W.J. (1995). "Induction of ectopic eyes by targeted expression of the eyeless gene in Drosophila".". Science 267 (5205): 1788–1792. doi:10.1126/science.7892602. PMID 7892602. [13] Tomarev, S.I.; Callaerts, P.; Kos, L.; Zinovieva, R.; Halder, G.; Gehring, W.; Piatigorsky, J. (1997). "Squid Pax-6 and eye development". Proc. Natl. Acad. Sci. USA 94 (6): 2421–2426. doi:10.1073/pnas.94.6.2421. PMC 20103. PMID 9122210. [14] Conway-Morris, S. (1998). The Crucible of Creation. Oxford: Oxford University Press. [15] Land, M.F.; Fernald, Russell D. (1992). "The evolution of eyes". Annu Rev Neurosci 15: 1–29. doi:10.1146/annurev.ne.15.030192.000245. PMID 1575438. [16] Eye-Evolution? (http:/ / library. thinkquest. org/ 28030/ eyeevo. htm) [17] Fernald, Russell D. (2001). The Evolution of Eyes: Where Do Lenses Come From? (http:/ / www. karger. com/ gazette/ 64/ fernald/ art_1_4. htm) Karger Gazette 64: "The Eye in Focus". [18] Kozmik, Zbynek; Ruzickova, Jana; Jonasova, Kristyna; Matsumoto, Yoshifumi; Vopalensky, Pavel; Kozmikova, Iryna; Strnad, Hynek; Kawamura, Shoji et al. (2008). "Assembly of the cnidarian camera-type eye from vertebrate-like components" (http:/ / www. pnas. org/ cgi/ reprint/ 0800388105v1. pdf) (PDF). Proceedings of the National Academy of Sciences 105 (26): 8989–8993. doi:10.1073/pnas.0800388105. PMC 2449352. PMID 18577593. . [19] Fernald, Russell D. (September 2006). "Casting a Genetic Light on the Evolution of Eyes". Science 313 (5795): 1914–1918. doi:10.1126/science.1127889. PMID 17008522. [20] "Vision Optics and Evolution" (http:/ / jstor. org/ stable/ 1311112). BioScience 39 (5): 298–307. 1 May 1989. doi:10.2307/1311112. ISSN 00063568. . [21] Wilson, M. (1978). "The functional organisation of locust ocelli". Journal of Comparative Physiology 124 (4): 297–316. doi:10.1007/BF00661380. [22] Wagner, H.J., Douglas, R.H., Frank, T.M., Roberts, N.W., and Partridge, J.C. (Jan. 27, 2009). "A Novel Vertebrate Eye Using Both Refractive and Reflective Optics". Current Biology 19 (2): 108–114. doi:10.1016/j.cub.2008.11.061. PMID 19110427. [23] Völkel, R; Eisner, M; Weible, K. J (June 2003). "Miniaturized imaging systems" (http:/ / www. suss-microoptics. com/ downloads/ Publications/ Miniaturized_Imaging_Systems. pdf) (PDF). Microelectronic Engineering 67-68 (1): 461–472. doi:10.1016/S0167-9317(03)00102-3. . [24] Gaten, Edward (1998). "Optics and phylogeny: is there an insight? The evolution of superposition eyes in the Decapoda (Crustacea)" (http:/ / dpc. uba. uva. nl/ ctz/ vol67/ nr04/ art01#FIGURE1). Contributions to Zoology 67 (4): 223–236. . [25] Ritchie, Alexander (1985). "Ainiktozoon loganense Scourfield, a protochordate? from the Silurian of Scotland". Alcheringa 9: 137. doi:10.1080/03115518508618961. [26] Mayer, G. (2006). "Structure and development of onychophoran eyes: What is the ancestral visual organ in arthropods?". Arthropod Structure and Development 35 (4): 231–245. doi:10.1016/j.asd.2006.06.003. PMID 18089073. [27] Ullrich-Luter, E. M.; Dupont, S.; Arboleda, E.; Hausen, H.; Arnone, M. I. (2011). "Unique system of photoreceptors in sea urchin tube feet". Proceedings of the National Academy of Sciences 108 (20): 8367–8372. doi:10.1073/pnas.1018495108. Eye 34 [28] Ali, Mohamed Ather; Klyne, M.A. (1985). Vision in Vertebrates. New York: Plenum Press. p. 8. ISBN 0-306-42065-1. [29] Land, M. F. (1989). "The eyes of hyperiid amphipods: relations of optical structure to depth" (http:/ / www. springerlink. com/ index/ P0P467K474307K3N. pdf) (PDF). Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology 164 (6): 751–762. doi:10.1007/BF00616747. . [30] Zeil, J. (1996). "The variation of resolution and of ommatidial dimensions in the compound eyes of the fiddler crab Uca lactea annulipes (Ocypodidae, Brachyura, Decapoda)" (http:/ / jeb. biologists. org/ cgi/ reprint/ 199/ 7/ 1569. pdf) (PDF). Journal of Experimental Biology 199 (7): 1569–1577. . [31] John C. Russ (2006). The Image Processing Handbook (http:/ / books. google. com/ ?id=Vs2AM2cWl1AC& pg=PT110& dq="50+ cycles+ per+ degree"+ acuity). CRC Press. ISBN 0849372542. OCLC 156223054. . "The upper limit (finest detail) visible with the human eye is about 50 cycles per degree,… (Fifth Edition, 2007, Page 94)" [32] Curtis D. Klaassen (2001). Casarett and Doull's Toxicology: The Basic Science of Poisons (http:/ / books. google. com/ ?id=G16riRjvmykC& pg=PA574& dq=cycles-per-degree+ acuity+ rat). McGraw-Hill Professional. ISBN 0071347216. OCLC 47965382. . [33] Robert E. Fischer; Biljana Tadic-Galeb. With contributions by Rick Plympton… (2000). Optical System Design (http:/ / books. google. com/ ?id=byx2Ne9cD1IC& pg=PA164& dq=eye+ resolution+ line-pairs+ 1. 7). McGraw-Hill Professional. ISBN 0071349162. OCLC 247851267. . [34] Barlow, Horace Basil; Mollon, J. D (1982). The Senses (http:/ / books. google. com/ ?id=kno6AAAAIAAJ& pg=PA98& vq=human+ spectral+ sensitivity& dq=eye+ visible+ spectrum). Cambridge: Univ. Pr.. pp. 98. ISBN 0521244749. . [35] Fernald, Russell D. (1997). "The Evolution of Eyes" (http:/ / www. stanford. edu/ group/ fernaldlab/ pubs/ 1997 Fernald. pdf) (PDF). Brain, Behaviour and Evolution 50 (4): 253–259. doi:10.1159/000113339. PMID 9310200. . [36] Goldsmith, T. H. (1990). "Optimization, Constraint, and History in the Evolution of Eyes" (http:/ / www. jstor. org/ stable/ pdfplus/ 2832368. pdf) (PDF). The Quarterly Review of Biology 65 (10000): 281–322. doi:10.1086/416840. PMID 2146698. . [37] Nilsson, E.; Arendt, D. (Dec 2008). "Eye Evolution: the Blurry Beginning". Current Biology 18 (23): R1096. doi:10.1016/j.cub.2008.10.025. ISSN 0960-9822. PMID 19081043. External links • Evolution of the eye (http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html) • Diagram of the eye (http://webvision.med.utah.edu/anatomy.html) • Webvision. The organisation of the retina and visual system. (http://webvision.med.utah.edu/) An in-depth treatment of retinal function, open to all but geared most toward graduate students. • Eye strips images of all but bare essentials before sending visual information to brain, UC Berkeley research shows (http://www.berkeley.edu/news/media/releases/2001/03/28_wers1.html) • A collection of resources for eye anatomy. (http://www.cotc.edu/studentlife/TutoringCenter/resourcessite/ heye.htm) • Anatomy of the eye - flash animated interactive. (http://www.lensshopper.com/eye-anatomy.asp) • Eyes (http://www.pharmacyproductinfo.com/eye.html)- Eyes are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain. • Detection of weak optical signals by the human visual system : Perspectives in Neuroscience and in Quantum Physics (http://home.etu.unige.ch/~alvarra0/Roberto_ALVAREZs_Personal_Page/About_Me_files/ Eye_project.pdf) • Macro photo of Eye (http://www.post35mm.com/photo.php?photo_id=32966) • Are Your Eyes Right (http://www.popsci.com/archive-viewer?id=oiUDAAAAMBAJ&pg=120&query=Vol. +144) February 1944 Popular Science Fork 35 Fork As a piece of cutlery or kitchenware, a fork is a tool consisting of a handle with several narrow tines on one end. The fork, as an eating utensil, has been a feature primarily of the West, whereas in East Asia chopsticks have been more prevalent. Today, forks are increasingly available throughout East Asia. The utensil (usually metal) is used to lift food to the mouth or to hold food in place while cooking or cutting it. Food can be lifted either by spearing it on the tines, or by holding it on top of the tines, which are often curved slightly. For this latter function, in the American style of fork etiquette, the fork is held with tines curving up; however, in continental style, the fork is held with the tines curving down. A fork is also shaped in the form of a trident but curved at the joint of the handle to the points. Assorted forks. From left to right: dessert fork, relish fork, salad fork, dinner fork, cold cuts fork, serving fork, carving fork. Blue Fork Sillhouette Fork 36 History Bronze forks made in Iran during the 8th or 9th century. The word 'fork' comes from the Latin furca, meaning "pitchfork." The ancient Greeks used[1] the fork as a serving utensil, and it is also mentioned in the Hebrew Bible, in the Book of I Samuel 2:13 ("The custom of the priests with the people was that when any man offered sacrifice, the priest’s servant came, while the fresh flesh was boiling, with a fork of three teeth in his hand..."). Bone forks had been found in the burial site of Qijia culture as well as later Chinese dynasties' tombs.[2] In the Roman Empire, bronze and silver forks were used, indeed many examples are displayed in museums around Europe.[3] [4] . But the use varied according to local customs, social class and the nature of food. After, in the western area, the fork is only occasionally mentioned in high medieval sources however linked to Byzantium. However, it was not commonly used in Western Europe until the 16th century when it became part of the etiquette. Before the fork was introduced, Westerners were reliant on the spoon and knife as the only eating utensils. Thus, people would largely eat food with their hands, calling for a common spoon when required. Members of the aristocracy would sometimes be accustomed to manners considered more proper and hold two knives at meals and use them both to cut and transfer food to the mouth, using the spoon for soups and broth. The earliest forks usually had only two tines, but those with numerous tines caught on quickly. The tines on these implements were straight, meaning the fork could only be used for spearing food and not for scooping it. The fork allowed meat to be easily held in place while being cut. The fork also allowed one to spike a piece of meat and shake off any undesired excess of sauce or liquid before consuming it. Wider use of the table fork in Western Europe was facilitated by two Byzantine imperial princesses who married into the Western aristocracy: the Empress Theophanu, wife of Emperor Otto II, in 972, and the Dogaressa Teodora Anna Dukaina Selvo, wife of the Doge of Venice Domenico Selvo, in 1075. By the 11th century, the table fork had made its way to Italy. In Italy, it became quite popular by the 14th century, being commonly used for eating by merchant and upper classes by 1600. It was proper for a guest to arrive with his own fork and spoon enclosed in a box called a cadena; this usage was introduced to the French court with Catherine de' Medici's entourage. Long after the personal table fork had become commonplace in France, at the supper celebrating the marriage of the duc de Chartres to Louis XIV's natural daughter in 1692, the seating was described in the court memoirs of Saint-Simon: "King James having his Queen on his right hand and the King on his left, and each with their cadenas." In Perrault's contemporaneous fairy tale of La Belle au bois dormant (1697), each of the fairies invited for the christening is presented with a splendid "Fork Holder." The fork's adoption in northern Europe was slower. Its use was first described in English by Thomas Coryat in a volume of writings on his Italian travels (1611), but for many years it was viewed as an unmanly Italian affectation. Some writers of the Roman Catholic Church expressly disapproved of its use, seeing it as "excessive delicacy": "God in his wisdom has provided man with natural forks — his fingers. Therefore it is an insult to Him to substitute artificial metallic forks for them when eating."[5] [6] It was not until the 18th century that the fork became commonly used in Great Britain, although some sources say forks were common in France, England and Sweden already by the early 17th century.[7] [8] The curved fork that is used in most parts of the world today, was developed in Germany in the mid 18th century. The standard four-tine design became current in the early 19th century. Fork 37 The 20th century also saw the emergence of the "spork", a utensil that is half-fork and half-spoon. With this new "fork-spoon", only one piece of cutlery is needed when eating (so long as no knife is required). The back of the spork is shaped like a spoon and can scoop food while the front has shortened tines like a fork, allowing spearing of food, making it convenient and easy to use. It has found popularity in fast food and military settings. Types of forks • Asparagus fork • Beef fork A fork used for picking up very thin slices of meat. This fork is shaped like a regular fork, but it is slightly bigger and the tines are curved outward. The curves are used for piercing the thin sliced beef. • Berry fork • Carving fork A 1908 design patent drawing for a spork, [9] from U.S. Patent D388,664 A two-pronged fork used to hold meat steady while it is being carved. They are often sold with carving knives or slicers as part of a carving set. • Cheese fork • Chip fork A two-pronged disposable fork, usually made out of sterile wood (though increasingly of plastic), specifically designed for the eating of chips (known as french fries in North America). • Cocktail fork A small fork resembling a trident, used for spearing cocktail garnishes such as olives. • Cold meat fork • Crab fork A short, sharp and narrow three-pronged or two-pronged fork designed to easily extract meat when consuming cooked crab. • Dessert fork (alternatively, pudding fork/cake fork in Great Britain) Any of several different special types of forks designed to eat desserts, such as a pastry fork. They usually have only three tines and are smaller than standard dinner forks. The leftmost tine may be widened so as to provide an edge with which to cut (though it is never sharpened). • Dinner fork • Fish fork • Fondue fork A narrow fork, usually having two tines, long shaft and an insulating handle, typically of wood, for dipping bread into a pot containing sauce • Fruit salad fork A fork used which is used to pick up pieces of fruit such as grapes, strawberries, melon and other varies types of fruit. • Ice cream fork • Knork A utensil combining characteristics of a knife and a fork • Lunch fork Fork 38 • • • • • Meat fork Olive fork Oyster fork Pastry fork Pickle fork A long handled fork used for extracting pickles from a jar, or an alternative name for a ball joint separator tool used to unseat a ball joint.[10] • • • • Pie fork Pitchfork Relish fork Salad fork Similar to a regular fork, but may be shorter, or have one of the outer tines shaped differently. Often, a "salad fork" in the silverware service of some restaurants (especially chains) may be simply a second fork; conversely, some restaurants may omit it, offering only one fork in their service. • Sporf A utensil combining characteristics of a spoon, a fork and a knife • Spork A utensil combining characteristics of a spoon and a fork • Tea fork • Toasting fork A fork, usually having two tines, very long metal shaft and sometimes an insulating handle, for toasting food over coals or an open flame Novelty forks • Extension Fork A long-tined fork with a telescopic handle, allowing for its extension or contraction. • Spaghetti fork A fork with a metal shaft loosely fitted inside a hollow plastic handle. The shaft protrudes through the top of the handle, ending in a bend that allows the metal part of the fork to be easily rotated with one hand while the other hand is holding the plastic handle. This supposedly allows spaghetti to be easily wound onto the tines. Electric variations of this fork have become more prevalent in modern times. Spaghetti fork Fork 39 References [1] "Forks" (http:/ / research. calacademy. org/ research/ anthropology/ utensil/ forks. htm). . [2] Needham (1986), volume 6 part 5 105–108 [3] "Fitzwilliam Museum - A combination Roman eating implement" (http:/ / www. fitzmuseum. cam. ac. uk/ opac/ search/ cataloguedetail. html?& priref=70534& _function_=xslt& _limit_=10). . [4] Sherlock, D. (1988) A combination Roman eating implement (1988). Antiquaries Journal [comments: 310-311, pl. xlix] [5] "A History of the Table Fork" (http:/ / www. maybe. org/ ~rodmur/ sca/ fork. html). . [6] "The Irrational Exhuberance of American Dining Etiquette" (http:/ / web. archive. org/ web/ 20091027152440/ http:/ / www. geocities. com/ rationalargumentator/ Dining_Etiquette. html). Archived from the original (http:/ / www. geocities. com/ rationalargumentator/ Dining_Etiquette. html) on 2009-10-27. . [7] http:/ / www. bookrags. com/ research/ knife-fork-and-spoon-woi/ [8] http:/ / www. popularhistoria. se/ o. o. i. s?id=170& vid=707 [9] http:/ / www. google. com/ patents?vid=D388,664 [10] http:/ / news. carjunky. com/ how_stuff_works/ how_to_change_ball_joints_ab1444. shtml Further reading • A history of the evolution of fork design can be found in: Henry Petroski, The Evolution of Useful things (1992); ISBN 0-679-74039-2 External links • Cutlery of the Middle Ages and Renaissance (http://www.larsdatter.com/cutlery.htm) Forks from the Greco-Roman era to the 17th century • http://www.urbandictionary.com/define.php?term=viljuska Gill A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a large surface area to the external environment. Many microscopic aquatic animals, and some that are larger but inactive, can absorb adequate oxygen through the entire surface of their bodies, and so can respire adequately without a gill. However, more complex or more active aquatic organisms usually require a gill or gills. Caribbean hermit crabs have modified gills that allow them to live in humid conditions Gills usually consist of thin filaments of tissue, branches, or slender tufted processes that have a highly folded surface to increase surface area. A high surface area is crucial to the gas exchange of aquatic organisms as water contains only 1/20 the dissolved oxygen that air does. Gill 40 With the exception of some aquatic insects, the filaments and lamellae (folds) contain blood or coelomic fluid, from which gases are exchanged through the thin walls. The blood carries oxygen to other parts of the body. Carbon dioxide passes from the blood through the thin gill tissue into the water. Gills or gill-like organs, located in different parts of the body, are found in various groups of aquatic animals, including mollusks, crustaceans, insects, fish, and amphibians. Note that, contrary to some misconceptions, gills do not break up water molecules into hydrogen and oxygen, but instead absorb the oxygen that is dissolved in the water. Invertebrate gills Respiration in the Echinodermata (includes starfish and sea urchins) is carried out using a very primitive version of gills called papulae. These thin protuberances on the surface of the body contain diverticula of the water vascular system. Crustaceans, molluscs, and some insects have gills that are tufted or plate-like structures at the surface of the body. The gills of other insects are tracheal, and also include both thin plates and tufted structures, and, in the larval dragon fly, the wall of the A live individual of the sea slug Pleurobranchaea caudal end of the alimentary tract (rectum) is richly supplied with meckelii. The gill (or ctenidium) is visible in this tracheae as a rectal gill. Water pumped into and out of the rectum view of the right-hand side of the animal provides oxygen to the closed tracheae. Aquatic insects use a tracheal gill, which contains air tubes. The oxygen in these tubes is renewed through the gills. Physical gills Physical gills are a type of structural adaptation common among some types of aquatic insects, which holds atmospheric oxygen in an area with small openings called spiracles. The structure (often called a plastron) typically consists of dense patches of hydrophobic setae on the body, which prevent water entry into the spiracles. The physical properties of the interface between the trapped air bubble and surrounding water accomplish gas exchange through the spiracles, almost as if the insect were in atmospheric air. Carbon dioxide diffuses into the surrounding water due to its high solubility, while oxygen diffuses into bubbles as the concentration within the bubble has been reduced by respiration, and nitrogen also diffuses out as its tension has been increased. Oxygen diffuses into the bubble at a higher rate than Nitrogen diffuses out. However, water surrounding the insect can become oxygen-depleted if there is no water movement, so many aquatic insects in still water actively direct a flow of water over their bodies. The physical gill mechanism allows aquatic insects with plastrons to remain constantly submerged. Examples include many beetles in the family Elmidae, aquatic weevils, and true bugs in the family Aphelocheiridae. Gill 41 Vertebrate gills The gills of vertebrates typically develop in the walls of the pharynx, along a series of gill slits opening to the exterior. Most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other. The gills are composed of comb-like filaments, the gill lamellae, which help increase their surface area for oxygen exchange.[1] When a fish breathes, it draws in a mouthful of water at regular intervals. Then it draws the sides of its throat together, forcing the water through the gill openings, so that it passes over the gills to the outside. Fish gill slits may be the evolutionary ancestors of the tonsils, thymus gland, and Eustachian tubes, as well as many other structures derived from the embryonic branchial pouches. The red gills of this common carp are visible as a result of a gill flap birth defect. Cartilaginous fish Sharks and rays typically have five pairs of gill slits that open directly to the outside of the body, though some more primitive sharks have six or seven pairs. Adjacent slits are separated by a cartilaginous gill arch from which projects a long sheet-like septum, partly supported by a further piece of cartilage called the gill ray. The individual lamellae of the gills lie on either side of the septum. The base of the arch may also support gill rakers, small projecting elements that help to filter food from the water.[2] Freshwater Fish Gills magnified 400 times A smaller opening, the spiracle, lies in front of the first gill slit. This bears a small pseudobranch that resembles a gill in structure, but only receives blood already oxygenated by the true gills.[2] The spiracle is thought to be homologous to the ear opening in higher vertebrates.[3] Most sharks rely on ram ventilation, forcing water into the mouth and over the gills by rapidly swimming forward. In slow-moving or bottom dwelling species, especially among skates and rays, the spiracle may be enlarged, and the [2] fish breathes by sucking water through this opening, instead of through the mouth. Chimaeras differ from other cartilagenous fish, having lost both the spiracle and the fifth gill slit. The remaining slits are covered by an operculum, developed from the septum of the gill arch in front of the first gill.[2] Gill 42 Bony fish In bony fish, the gills lie in a branchial chamber covered by a bony operculum. The great majority of bony fish species have five pairs of gills, although a few have lost some over the course of evolution. The operculum can be important in adjusting the pressure of water inside of the pharynx to allow proper ventilation of the gills, so that bony fish do not have to rely on ram ventilation (and hence near constant motion) to breathe. Valves inside the mouth keep the water from escaping.[2] The gill arches of bony fish typically have no septum, so that the gills alone project from the arch, supported by individual gill rays. Some species retain gill rakers. Though all but the most primitive bony fish The red gills inside a detached tuna head lack a spiracle, the pseudobranch associated with it often remains, being (viewed from behind) located at the base of the operculum. This is, however, often greatly reduced, consisting of a small mass of cells without any remaining gill-like structure.[2] Marine teleosts also use gills to excrete electrolytes. The gills' large surface area tends to create a problem for fish that seek to regulate the osmolarity of their internal fluids. Saltwater is less dilute than these internal fluids, so saltwater fish lose large quantities of water osmotically through their gills. To regain the water, they drink large amounts of seawater and excrete the salt. Freshwater is more dilute than the internal fluids of fish, however, so freshwater fish gain water osmotically through their gills.[2] Other vertebrates Lampreys and hagfish do not have gill slits as such. Instead, the gills are contained in spherical pouches, with a circular opening to the outside. Like the gill slits of higher fish, each pouch contains two gills. In some cases, the openings may be fused together, effectively forming an operculum. Lampreys have seven pairs of pouches, while hagfishes An Alpine newt larva showing the external gills, may have six to fourteen, depending on the species. In the hagfish, the which flare just behind the head pouches connect with the pharynx internally. In adult lampreys, a separate respiratory tube develops beneath the pharynx proper, separating food and water from respiration by closing a valve at its anterior end.[2] Tadpoles of amphibians have from three to five gill slits that don't contain actual gills. There is usually no spiracle or true operculum, though many species have an operculum-like structure. Instead of internal gills, they develop three feathery external gills that grow from the outer surface of the gill arches. Sometimes adults retain these, but they usually disappear at metamorphosis. Lungfish larvae also have external gills, as does the primitive ray-finned fish Polypterus, though the latter has a structure different than amphibians.[2] Gill 43 Branchia Branchia (pl. branchiæ) is the Ancient Greek naturalists' name for gills. Galen observed that fish had multitudes of openings (foramina), big enough to admit gases, but too fine to give passage to water. Pliny the Elder held that fish respired by their gills, but observed that Aristotle was of another opinion.[4] The word branchia comes from the Greek βράγχια, "gills", plural of βράγχιον (in singular, meaning a fin).[5] References [1] Andrews, Chris; Adrian Exell, Neville Carrington (2003). Manual Of Fish Health. Firefly Books. [2] Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 316–327. ISBN 0-03-910284-X. [3] Laurin M. (1998): The importance of global parsimony and historical bias in understanding tetrapod evolution. Part I-systematics, middle ear evolution, and jaw suspension. Annales des Sciences Naturelles, Zoologie, Paris, 13e Série 19: pp 1-42. [4] This article incorporates content from the 1728 Cyclopaedia, a publication in the public domain. [5] "Branchia". Oxford English Dictionary. Oxford University Press. 2nd Ed. 1989. Grater Grater A box grater with multiple grating surfaces. Box grater with vegetable slicing surface displayed. A grater (also known as a shredder in parts of the eastern United States) is a kitchen utensil used to grate foods into fine pieces. It was invented by François Boullier in the 1540s. Grater 44 Uses Several types of graters feature different sizes of grating slots, and can therefore aid in the preparation of a variety of foods. They are commonly used to grate cheese and lemon or orange peel (to create zest), and can also be used to grate other soft foods. They are commonly used in the preparation of toasted cheese, Welsh rarebit, and macaroni and cheese. In Slavic cuisine, graters are commonly used to grate potatoes, for preparation of, e.g., draniki, bramborak or potato babka. In tropical nations, graters are also used to grate coconut meat. In Jamaica, a coconut grater is used as a traditional musical instrument[1] (along with drums, fife, and other instruments) in the performance of kumina, jonkanoo, and sometimes mento. History The cheese grater was invented by Issac Hunt in the 1540s so hard cheeses could still be used. Variants There are also complex food-processing machines with grater-like mechanisms. These mechanisms rotate by the turn of a cluster or electric motor. Media A microplane A zest grater Porcelain ginger grater Sharkskin grater A nutmeg grater Multiple graters Grater 45 In popular culture • In The Sopranos episode, "Mergers and Acqusitions", Valentina La Paz reports, in disgust, to Tony Soprano that in lieu of having conventional sexual relations, Soprano family mob captain, Ralph Cifaretto, asks her to scrape a cheese grater across his back and pour hot candle wax on his testicles. • In recent times, the term 'cheese grating' has evolved, as slang, to mean 'screen cheating' in video games. Therefore a 'cheese grater' can also reference a person who actively 'screen cheats'. For example: Mark grates tonnes of cheese in Halo: Reach. • Comedian Mitch Hedberg performed a joke in which he stated that the negative name of cheese grater would be "a sponge ruiner."[2] References [1] Brad Fredericks. "American Rhythm and Blues Influence on Early Jamaican Musical Style" (http:/ / debate. uvm. edu/ dreadlibrary/ fredericks. html). . Retrieved 2007-07-14. [2] Mitch Hedberg. "Mitch Hedberg - Cheese Shredder" (http:/ / www. funnyordie. com/ videos/ 01ebe428cd/ mitch-hedberg-cheese-shredder-from-standupfan). . Retrieved 2011-06-25. Handle (grip) A handle is a part of, or attachment to, an object that can be moved or used by hand. The design of each type of handle involves substantial ergonomic issues, even where these are dealt with intuitively or by following tradition. Alternatively, the term "handle" can be used to refer to the fleshy portion of the lower human buttock. General design criteria The three nearly universal requirements of are: 1. Sufficient strength to support the object, or to otherwise transmit the force involved in the task the handle serves. 2. Sufficient length to permit the hand or hands gripping it to reliably exert that force. 3. Sufficiently small circumference to permit the hand or hands to surround it far enough to grip it as solidly as needed to exert that force. Other requirements may apply to specific handles: • A sheath or coating on the handle that provides friction against the hand, reducing the gripping force needed to achieve a reliable grip. • Designs such as recessed car-door handles, reducing the chance of accidental operation, or simply the inconvenience of "snagging" the handle. • Sufficient circumference to distribute the force comfortably and safely over the hand. An example where this requirement is almost the sole purpose for a handle's existence is the handle that consists of two pieces: a hollow wooden cylinder about the diameter of a finger and a bit longer than one hand-width, and a stiff wire that passes through the center of the cylinder, has two right angles, and is shaped into a hook at each end. This handle permits comfortable carrying, with otherwise bare hands, of a heavy package, suspended on a tight string that passes around the top and bottom of it: the string is strong enough to support it, but the pressure the string would exert on fingers that grasped it directly would often be unacceptable. • Design to thwart unwanted access, for example, by children or thieves. In these cases many of the other requirements may have reduced importance. For example, a child-proof doorknob can be difficult for even an adult to use. Handle (grip) 46 Pull handles One major category of handles are pull handles, where one or more hands grip the handle or handles, and exert force to shorten the distance between the hands and their corresponding shoulders. The three criteria stated above are universal for pull handles. Many pull handles are for lifting, mostly on objects to be carried. Horizontal pull handles are widespread, including drawer pulls, handles on latchless doors and the outside of car doors. The inside controls for opening car doors from inside are usually pull handles, although their function of permitting the door to be pushed open is Many drawers use pull handles. accomplished by an internal unlatching linkage. Two kinds of pull handles may involve motion in addition to the hand-focused motions described: • Pulling the starting cord on a small internal-combustion engine may, besides moving the hand toward the shoulder, also exploit simultaneously pushing a wheeled vehicle away with the other hand, stepping away from the engine, and/or standing from a squat. • Some throwing motions, as in a track-and-field hammer throw, involve pulling on a handle against centrifugal force (without bringing it closer), in the course of accelerating the thrown object by forcing it into circular motion. Twist handles Another category of hand-operated device requires grasping (but not pulling) and rotating the hand and either the lower arm or the whole arm, about their axis. When the grip required is a fist grip, as with a door handle that has an arm rather than a knob to twist, the term "handle" unambiguously applies. Another clear case is a rarer device seen on mechanically complicated doors like those of airliners, where (instead of the whole hand moving down as it also rotates, on the door handles just described) the axis of rotation is between the thumb and the outermost fingers, so the thumb moves up if the outer fingers move down. Many doors use twist handles. In first-world countries, handles often twist in a clockwise fashion, while in second-world countries, the twist of handles is often counterclockwise. However, most double doors and double windows are used with one handle clockwise and the other handle counterclockwise. This double twisting is often effective on windows, doors, cabinets, and faucets. Handles for wide-range motion The handles of bicycle grips, club-style weapons, shovels and spades, axes, hammers, mallets and hatchets, baseball bats, rackets, golf clubs, and croquet mallets involve a much greater range of ergonomic issues. References Head 47 Head In anatomy, the head of an animal is the rostral part (from anatomical position) that usually comprises the brain, eyes, ears, nose and mouth (all of which aid in various sensory functions, such as sight, hearing, smell, and taste). Some very simple animals may not have a head, but many bilaterally symmetric forms do. Cultural importance For humans, the head and particularly the face are the main distinguishing feature between different people, due to their easily discernible features such as hair and eye color, nose, eye and mouth shapes, wrinkles, etc. Human faces are easily differentiable to us due to our brains' predispositions toward discriminating human facial forms. When observing a relatively unfamiliar species, all faces seem nearly identical, and human infants are biologically programmed to recognize subtle differences in anthropic facial features. The human head drawn by Leonardo da Vinci People who are more intelligent than normal are sometimes depicted in cartoons as having bigger heads, as a way of indicating that they have a larger brain; in science fiction, an extraterrestrial having a big head is often symbolic of high intelligence. Outside of this symbolic depiction, however, advances in neurobiology have shown that the functional diversity of the brain means that a difference in overall brain size is not a reliable indicator of how much, if any, difference in overall intelligence exists between two humans.[1] A cheetah's head The head is a source for many metaphors and metonymies in human language, including referring to things typically near the human head ( "the head of the bed"), things physically similar to the way a head is arranged spatially to a body ("the head of the table"), metaphorically ("the head of the class/FBI"), and things that represent some characteristic we associate with the head, such as intelligence ("there are a lot of good heads in this company"). These examples are all from English, but only some are possible expressions in other languages (depending on the language). (See Lakoff and Johnson 1980, 1999) Ancient Greeks had a method for evaluating sexual attractiveness based on the Golden Ratio, part of which included measurements of the head. Head 48 Clothing In many cultures, covering the head is seen as a sign of respect. Often, some or all of the head must be covered and veiled when entering holy places, or places of prayer. For many centuries, women in Europe, the Middle East, and South Asia have covered their hair as a sign of modesty. This trend has changed drastically in Europe in the 20th century, although is still observed in other parts of the world. In addition, a number of religious paths require men to wear specific head clothing—such as the Islamic Taqiyah, Jewish yarmulke, or the Sikh turban; or Muslim women, who cover their hair, ears, and neck with a scarf. Original caption: on sale in the bazar in Isfahan People may cover the head for other reasons. A hat, is a piece of clothing covering just the top of the head. This may be part of a uniform, such as a Police uniform, a protective device such as a hard hat, a covering for warmth, or a fashion accessory. Different headpieces can also signify status, origin, religious/spiritual beliefs, social grouping, occupation, and fashion choices. Anthropometry Static adult human Anthropometryphysical characteristics of the head. Notes [1] Brain Size and Intelligence (http:/ / www. ncbi. nlm. nih. gov/ books/ bv. fcgi?rid=neurosci. box. 1833) References • Campbell, Bernard Grant. Human Evolution: An Introduction to Man's Adaptations (4th edition), ISBN 0-202-02042-8 Hoof 49 Hoof A hoof ( /ˈhuːf/ or /ˈhʊf/), plural hooves ( /ˈhuːvz/ or /ˈhʊvz/) or hoofs ( /ˈhʊfs/), is the tip of a toe of an ungulate mammal, strengthened by a thick horny (keratin) covering. The hoof consists of a hard or rubbery sole, and a hard wall formed by a thick nail rolled around the tip of the toe. The weight of the animal is normally borne by both the sole and the edge of the hoof wall. Hooves grow continuously, and are constantly worn down by use. Most even-toed ungulates (such as sheep, goats, deer, cattle, bison and pigs) have two main hooves on each foot, together called a cloven hoof. Most of these cloven-hoofed Cloven hooves of Roe Deer (Capreolus capreolus), with dew claws animals also have two smaller hoofs called dew-claws a little further up the leg – these are not normally used for walking, but in some species with larger dew-claws (such as deer and pigs) they may touch the ground when running or jumping, or if the ground is soft. Other cloven-hoofed animals (such as giraffes and pronghorns) have no dew claws. In some so-called "cloven-hoofed" animals such as camels, there are no hooves proper – the toe is softer, and the hoof itself is reduced to little more than a nail. Some odd-toed ungulates (equids) have one hoof on each foot; others (including rhinoceroses, tapirs and many extinct species) have (or had) three hoofed or heavily nailed toes, or one hoof and two dew-claws. The tapir is a special case, with three toes on each hind foot and four toes on each front foot. Sagittal section of a wild horsehoof. Pink: soft tissues; light gray: bone; blue: tendons; red: corium; yellow: digital cushion; dark gray: frog; orange: sole; brown: walls camel hoof Sheet plastinate of a horse hoof. Rear foot of a giraffe (no dew claws) Rear hooves of a horse Hoof 50 Uses Hooves have historical significance in ceremonies and games. They have been used in burial ceremonies[1] , in the Dart Golf game Dolf.[2] and in the song Hooves of the Ibex by Wormhole.[3] References [1] M. E. Robertson-Mackay (1980). A head and hooves burial beneath a round barrow, with other Neolithic and Bronze Age sites on Hemp Knoll, near Avebury, Wiltshire (http:/ / www. zotero. org/ samwalsh/ items/ 7EBE4GDE). Proceedings of the Prehistoric Society. . [2] "WDFF Playing & Tournament Rules" (http:/ / www. dolfdarts. com/ the-rules-of-dolf). 1999. . [3] "Wormhole" (http:/ / www. myspace. com/ wormholemusic). 2007. . Horn (anatomy) A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn (keratin and other proteins) surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae (pronghorn) and Bovidae (cattle, goats, antelope etc.). One pair of horns is usual, but two pairs occur in a few wild species and in a few domesticated breeds of sheep. Partial or deformed horns in livestock are called scurs. Horns usually have a curved or spiral shape, often with ridges or fluting. In many species only males have horns. Horns start to grow soon after birth, and continue to grow throughout the life of the animal (except in pronghorns, which shed the outer layer annually, but retain the bony core). Similar growths on other parts of the body are not usually called horns, but spurs, claws or hoofs, depending on the part of the body on which they occur. Other hornlike growths The term "horn" is also popularly applied to other hard and pointed features attached to the head of animals in various other families: A goat with spiral horns • Giraffidae: Giraffes have one or more pairs of bony bumps on their heads, called ossicones. These are covered with furred skin. • Cervidae: Most deer have antlers, which are not true horns. When fully developed, antlers are dead bone without a horn or skin covering; they are borne only by adults (usually males) and are shed and regrown each year. • Rhinocerotidae: The "horns" of rhinoceroses are made of keratin and grow continuously, but do not have a bone core. • Chamaeleonidae: Many chameleons, most notably the Jackson's Chameleon, possess horns on their skulls, and have a keratin covering. Horn (anatomy) 51 • Ceratopsidae: The "horns" of the Triceratops were extensions of its skull bones although debate exists over whether they had a keratin covering. • Horned lizards (Phrynosoma): These lizards have horns on their heads which have a hard keratin covering over a bony core, like mammalian horns. • Insects: Some insects (such as rhinoceros beetles) have horn-like structures on the head or thorax (or both). These are pointed outgrowths of the hard chitinous exoskeleton. Some (such as stag beetles) have greatly enlarged jaws, also made of chitin. • Canidae: Golden jackals are known to occasionally develop a horny growth on the skull, which is associated with magical powers in south-eastern Asia.[1] [2] Many mammal species in various families have tusks, which often serve the same functions as horns, but are in fact oversize teeth. These include the Moschidae (Musk deer, which are ruminants), Suidae (Wild Boars), Proboscidea (Elephants), Monodontidae (Narwhals) and Odobenidae (Walruses). Polled animals or pollards are those of normally-horned (mainly domesticated) species whose horns have been removed, or which have not grown. In some cases such animals have small horny growths in the skin where their horns would be – these are known as scurs. On humans Cutaneous horns are the only examples of horns growing on people. They are believed to be caused by exposure to radiation. They are most often benign growths and can be removed by a razor. Cases of people growing horns have been historically described, sometimes with mythical status. Researchers have not however discovered photographic evidence of the phenomenon.[3] There are human cadaveric A Hebridean sheep with one horn on one side and two on the other. specimens that show outgrowings, but these are instead classified as osteomas or other excrescences.[3] Theoretically, there may be children born with horns which are corrected with early surgical intervention. The phenomenon of humans with horns has been observed in countries lacking advanced medicine. There are living people, several in China, with cases of cutaneous horns, most common in the elderly[4] . Some people, notably The Enigma, have horn implants; that is, they have implanted silicone beneath the skin as a [5] form of body modification. Horn (anatomy) 52 Animal uses of horns Animals have a variety of uses for horns and antlers, including defending themselves from predators and fighting members of their own species for territory, dominance or mating priority. Horns are usually present only in males but in some species, females too may possess horns. It has been theorized by researchers that taller species living in the open are more visible from longer distances and more likely to benefit from horns to defend themselves against predators. Female bovids that are not hidden from predators due to their large size or open Savannah like habitat are more likely to bear horns than small or camouflaged species.[6] Both male and female African buffaloes bear horns In addition, horns may be used to root in the soil or strip bark from trees. In animal courtship many use horns in displays. For example, the male blue wildebeest reams the bark and branches of trees to impress the female and lure her into his territory. Some animals with true horns use them for cooling. The blood vessels in the bony core allow the horns to function as a radiator. Human uses of horns • Horned animals are sometimes hunted so their mounted head or horns can be displayed as a hunting trophy or as decorative objects. This practice can be considered controversial, especially as some animals are threatened or endangered due to reduced populations partially from pressures of such hunting. • Some cultures use bovid horns as musical instruments, for example the shofar. These have evolved into brass instruments in which, unlike the trumpet, the bore gradually increases in width through most of its length—that is to say, it is conical rather than cylindrical. These are called horns, though now made of metal. Water buffalo horn used as a hammer with cleaver to cut fish in southeast China. • Drinking horns are bovid horns removed from the bone core, cleaned and polished and used as drinking vessels. (See also the legend of the Horn of plenty, or Cornucopia). It has been suggested that the shape of a natural horn was also the model for the rhyton, a horn-shaped drinking vessel.[7] • Powder horns were originally bovid horns fitted with lids and carrying straps, used to carry gunpowder. Powder flasks of any material may be referred to as powder horns. • Antelope horns are used in traditional Chinese medicine. • Horns consist of keratin, and the term "horn" is used to refer to this material, sometimes including similarly solid keratin from other parts of animals, such as hoofs. Horn may be used as a material in tools, furniture and decoration, among other uses. In these applications, horn is valued for its hardness, and it has given rise to the expression hard as horn. Horn is somewhat thermoplastic and (like tortoiseshell) was formerly used for many purposes where plastic would now be used. Horn may be used to make glue. • Horn bows are bows made from a combination of horn, sinew and usually wood. These materials allow more energy to be stored in a short bow than wood alone. • Ivory comes from the teeth of animals, not horns. Horn (anatomy) • "Horn" buttons are usually made from deer antlers, not true horn. References [1] Sketches of the natural history of Ceylon by Sir James Emerson Tennent, published by Longman, Green, Longman, and Roberts, 1861 [2] Mammals of Nepal: (with reference to those of India, Bangladesh, Bhutan and Pakistan) by Tej Kumar Shrestha, published by Steven Simpson Books, 1997, ISBN 0952439069 [3] Tubbs, John C. III; Smyth, Matthew D.; Wellons; Blount, Jeffrey P.; Oakes, W. Jerry (June 2003). "Human horns: a historical review and clinical correlation". Neurosurgery 52 (6): 1443–1448. doi:10.1227/01.NEU.0000064810.08577.49. PMID 12762889. (Literature Reviews) [4] . http:/ / www. stern. de/ wissen/ mensch/ ungewoehnliche-operation-aerzte-befreien-frau-von-horn-1682189. html. [5] Johann, Hari (2002-03-11). "Johann Hari on the bizarre world of radical plastic surgery" (http:/ / www. guardian. co. uk/ society/ 2002/ mar/ 11/ health. lifeandhealth). London: Guardian News and Media. . Retrieved 2010-05-04. [6] http:/ / www. physorg. com/ news172428997. html [7] Chusid, Hearing Shofar: The Still Small Voice of the Ram's Horn, 2009, Chapter 3-6 - Ram's Horn of Passover <http://www.hearingshofar.com>. The book also posits that the ancient Hebrews and neighboring tribes used horns as weapons and as utensils. External links • A site with information about the history of the cow horn as a musical instrument. (http://www.ancientmusic. co.uk/ancientinstruments/Blowing_Horns.html) 53 Human leg 54 Human leg Human leg Lateral aspect of right leg Latin membrum inferios MeSH Leg [1] Dorlands/Elsevier Leg [2] The human leg is the entire lower extremity or limb[3] [4] of the human body, including the foot, thigh and even the [5] [6] [7] to the section of the lower limb hip or gluteal region, the precise definition in human anatomy refers extending between the knee and the ankle. Legs are used for standing, walking, jumping, running, kicking, and similar activities, and constitute a significant portion of a person's mass. Anatomy In human anatomical terms, the leg is the part of the lower limb that lies between the knee and the ankle,[8] the thigh is between the hip and knee and the term "lower limb" is used to describe the colloquial leg. This article generally follows the common usage. The leg from the knee to the ankle is called the cnemis (née'mis) or crus. The calf is the back portion and the shin is the front. Evolution has provided the human body with two distinct features: the specialization of the upper limb for visually guided manipulation and the lower limb's development into a mechanism specifically adapted for efficient bipedal gait. While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy. The human adaption to bipedalism is not limited to the leg, however, but has also affected the location of the body's center of gravity, the reorganisation of internal organs, and the form and biomechanism of the trunk. In humans, the double S-shaped vertebral column acts as a shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are Comparison between human and exceptionally long and powerful as a result of their exclusive specialization to gorilla skeletons. (Gorilla in support and locomotion — in orangutans the leg length is 111% of the trunk; in non-natural stretched posture.) chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to bipedalism, most substantially the gluteal muscles, the extensors of the knee joint, and the calf muscles.[9] Human leg 55 See also: Human skeletal changes due to bipedalism Skeleton The major (long) bones of the human leg are the femur (thighbone), tibia (shinbone), and fibula (the smaller, rear calf bone). The patella (kneecap) is the bone in front of the knee. Most of the leg skeleton has bony prominences and margins that can be palpated, notable exceptions being the hip joint, and the neck and shaft of femur. Many of these anatomical landmarks are used to define the extent of the leg: most notably the anterior superior iliac spine, the greater trochanter, the superior margin of the medial condyle of tibia, and the medial malleolus.[10] In the normal case, the large joints of the lower limb are aligned on a straight line which represents the mechanical longitudinal axis of the leg, the Mikulicz line. This line stretches from the hip joint (or more precisely the head of the femur), Bones of the leg through the knee joint (the intercondylar eminence of the tibia), and down to the center of the ankle (the ankle mortise, the fork-like grip between the medial and lateral malleoli). In the tibial shaft, the mechanical and anatomical axes coincide, but in the femoral shaft they diverge 6°, resulting in the femorotibial angle of 174° in a leg with normal axial alignment. A leg is considered straight when, with the feet brought together, both the medial malleoli of the ankle and the medial condyles of the knee are touching. Divergence from the normal femorotibial angle is called genu varum if the center of the knee joint is lateral to the mechanical axis (intermalleolar distance exceeds 3 cm), and genu valgum if it is medial to the mechanical axis (intercondylar distance exceeds 5 cm). These conditions impose unbalanced loads on the joints and stretching of either the thigh's adductors and abductors.[11] The angle of inclination formed between the neck and shaft of the femur, the collodiaphysial angle, varies with age—about 150° in the newborn, it gradually decreases to 126-128° in adults, to reach 120° in old age. Pathological changes in this angle results in abnormal posture of the leg: A small angle produces coxa vara and a large angle in coxa valga; the latter is usually combined with genu varum and coxa vara leads genu valgum. Additionally, a line drawn through the femoral neck superimposed on a line drawn through the femoral condyles forms an angle, the torsion angle, which makes it possible for flexion movements of the hip joint to be transposed into rotary movements of the femoral head. Abnormally increased torsion angles results in a limb turned inward and a decreased angle in a limb turned outward; both cases resulting in a reduced range of mobility.[12] Muscles Hip Human leg 56 Function of hip muscles[13] Movement Muscles (In order of importance) Lateral rotation • Sartorius • Gluteus maximus • Quadratus femoris • Obturator internus • Gluteus medius and minimus • Iliopsoas (with psoas major♣) • Obturator externus • All functional adductors except gracilis* and pectineus • Piriformis Medial rotation • Gluteus medius and minimus (anterior fibers) • Tensor fascia latae* • Adductor magnus (long medial fibers) • Pectineus (with leg abducted) Extension • Gluteus maximus • Gluteus medius and minimus (dorsal fibers) • Adductor magnus • Piriformis • Semimembranosus* • Semitendinousus* • Biceps femoris* (long head) Flexion • Iliopsoas (with psoas major♣) • Tensor fascia latae* • Pectineus • Adductor longus • Adductor brevis • Gracilis* • Rectus femoris* • Sartorius* Abduction • Gluteus medius • Tensor fascia latae* • Gluteus maximus (fibers to fascia lata) • Gluteus minimus • Piriformis • Obturator internus Human leg 57 Adduction • Adductor magnus (with adductor minimus) • Adductor longus • Adductor brevis • Gluteus maximus (fibers to gluteal tuberosity) • Gracilis • Pectineus • Quadratus femoris • Obturator externus • Semitendinosus* Notes ♣ Also act on vertebral joints. * Also act on knee joint. There are several ways of classifying the muscles of the hip: (1) By location or innervation (ventral an dorsal divisions of the plexus layer); (2) by development on the basis of their points of insertion (a posterior group in two [14] layers and an anterior group); and (3) by function (i.e. extensors, flexors, adductors, and abductors). Some hip muscles also act on either the knee joint or on vertebral joints. Additionally, because the area of origin and insertion of many of these muscles are very extensive, these muscles are often involved in several very different movements. In the hip joint, lateral and medial rotation occur along the axis of the limb; extension (also called dorsiflexion or retroversion) and flexion (anteflexion or anteversion) occur along a transverse axis; and abduction and adduction occur about a sagittal axis.[13] The anterior dorsal hip muscles are the iliopsoas, a group of two or three muscles with a shared insertion on the lesser trochanter of the femur. The psoas major originates from the last vertebra and along the lumbar spine to stretch down into the pelvis. The iliacus originates on the iliac fossa on the interior side of the pelvis. The two muscles unite to form the iliopsoas muscle which is inserted on the lesser trochanter of the femur. The psoas minor, only present in about 50 per cent of subjects, originates above psoas major to stretch obliquely down to its insertion on the interior side of the major muscle.[15] The posterior dorsal hip muscles are inserted on or directly below the greater trochanter of the femur. The tensor fascia latae, stretching from the anterior superior iliac spine down into the iliotibial tract, presses the head of the femur into the acetabulum but also flexes, rotates medially, and abducts to hip joint. The piriformis originates on the anterior pelvic surface of the sacrum, passes through the greater sciatic foramen, and inserts on the posterior aspect of the tip of the greater trochanter. In a standing posture it is a lateral rotator, but it also assists extending the thigh. The gluteus maximus has its origin between (and around) the iliac crest and the coccyx from where one part radiates into the iliotibial tract and the other stretches down to the gluteal tuberosity under the greater trochanter. The gluteus maximus is primarily an extensor and lateral rotator of the hip joint, and it comes into action when climbing stairs or rising from a sitting to standing posture. Furthermore, the part inserted into the fascia latae abducts and the part inserted into the gluteal tuberosity adducts the hip. The two deep glutei muscles, the gluteus medius and minimus, originate on the lateral side of the pelvis. The medius muscle is shaped like a cap. Its anterior fibers act as a medial rotator and flexor; the posterior fibers as a lateral rotator and extensor; and the entire muscle abducts the hip. The minimus has similar functions and both muscles are inserted onto the greater trochanter.[16] Human leg The ventral hip muscles function as lateral rotators and play an important role in the control of the body's balance. Because they are stronger than the medial rotators, in the normal position of the leg, the apex of the foot is pointing outward to achieve better support. The obturator internus originates on the pelvis on the obturator foramen and its membrane, passes through the lesser sciatic foramen, and is inserted on the trochanteric fossa of the femur. "Bent" over the lesser sciatic notch, which acts as a Muscles of hip fulcrum, the muscle forms the strongest lateral rotators of the hip together with the gluteus maximus and quadratus femoris. When sitting with the knees flexed it acts as an abductor. The obturator externus has a parallel course with its origin located on the posterior border of the obturator foramen. It is covered by several muscles and acts as a lateral rotator and a weak adductor. The inferior and superior gemelli represent marginal heads of the obturator internus and assist this muscle. The three muscles have been referred to as the triceps coxae. The quadratus femoris originates at the ischial tuberosity and is inserted onto the intertrochanteric crest between the trochanters. This flattened muscle act as a strong lateral rotator and adductor of the thigh.[17] The adductor muscles of the thigh are innervated by the obturator nerve, with the exception of pectineus which receives fibers from the femoral nerve, and the adductor magnus which receives fibers from the tibial nerve. The gracilis arises from near the pubic symphysis and is unique among the adductors in that it reaches past the knee to attach on the medial side of the shaft of the tibia, thus acting on two joints. It share its distal insertion with the sartorius and semitendinosus, all three muscles forming the pes anserinus. It is the most medial muscle of the adductors, and with the thigh abducted its origin can be clearly seen arching under the skin. With the knee extended, it adducts the thigh and flexes the hip. The pectineus has its origin on the iliopubic eminence laterally to the gracilis and, rectangular in shape, extends obliquely to attach immediately behind the lesser trochanter and down the pectineal line and the proximal part of the linea aspera on the femur. It is a flexor of the hip joint, and an adductor and a weak medial rotator of the thigh. The adductor brevis originates on the inferior ramus of the pubis below the gracilis and stretches obliquely below the pectineus down to the upper third of the linea aspera. Except for Hip adductors being an adductor, it is a lateral rotator and weak flexor of the hip joint.[18] The adductor longus has its origin at superior ramus of the pubis and inserts medially on the middle third of the linea aspera. Primarily an adductor, it is also responsible for some flexion. The adductor magnus has its origin just behind the longus and lies deep to it. Its wide belly divides into two parts: One is inserted into the linea aspera and the tendon of the other reaches down to adductor tubercle on the medial side of the femur's distal end where it forms an intermuscular septum that separates the flexors from the extensors. Magnus is a powerful adductor, especially active when crossing legs. Its superior part is a lateral rotator but the inferior part acts as a medial rotator on the flexed leg when rotated outward and also extends the hip joint. The adductor minimus is an incompletely separated subdivision of the adductor magnus. Its origin forms an anterior part of the magnus and distally it is inserted on the linea aspera above the magnus. It acts to adduct and lateral rotate the femur.[19] Thigh 58 Human leg 59 Function of knee muscles[20] Movement Muscles (In order of importance) Extension • Quadriceps femoris • Tensor fascia latae* Flexion • Semimembranosus • Semitendinosus • Biceps femoris • Gracilis • Sartorius • Popliteus • Gastrocnemius Medial rotation • Semimembranosus • Semitendinosus • Gracilis • Sartorius • Popliteus Lateral rotation • Biceps femoris • Tensor fascia latae* *Insignificant assistance. The muscles of the thigh can be classified into three groups according to their location: anterior and posterior muscles and the adductors (on the medial side). All adductors (see above) except gracilis insert on the femur and therefore act only on the hip joint. The majority of the thigh muscles, the "true" thigh muscles, are insert on the leg (either the tibia or the fibula) and thus act primarily on the knee joint. Functionally, the extensors lie anteriorly on the thigh and are distinguished from flexors on the posterior side. Even though the sartorius flexes the knee, it is ontogenetically considered an extensor since its displacement is secondarily.[14] Most of the adductors act exclusively on the hip joint, so functionally they qualify as hip muscles. Anterior and posterior thigh muscles. Of the anterior thigh muscles the largest are the four muscles of the quadriceps femoris. The central rectus femoris which is surrounded by the three vasti: The vastus intermedius, medialis, and lateralis. Rectus femoris is attached to the pelvis with two tendons, while the vasti are inserted to the femur. All four muscles unite in a common tendon inserted into the patella from where the patellar ligament extends it down to the tibial tuberosity. Fibers from the medial and lateral vasti form two retinacula that stretch past the patella on either sides down to the condyles of the tibia. The quadriceps is the knee extensor, but the rectus femoris additionally flexes the hip joint, and articular muscle of the knee protects the articular capsule of the knee joint from being nipped during extension. The sartorius runs superficially and obliquely down on the anterior side of the thigh, from the anterior superior iliac spine to the pes anserinus on the medial side of the knee, from where it is further extended into the crural fascia. The sartorius acts as a flexor on both the hip and knee, but, due to its oblique course, also contributes to medial rotation of the leg Human leg 60 as one of the pes anserinus muscles (with the knee flexed), and to lateral rotation of the hip joint.[21] There are four posterior thigh muscles. The biceps femoris has two heads: The long head has its origin on the ischial tuberosity together with the semitendinosus and acts on two joints. The short head originates from the middle third of the linea aspera on the shaft of the femur and the lateral intermuscular septum of thigh, and acts on only one joint. These two heads unite to form the biceps which inserts on the head of the fibula. The biceps flexes the knee joint and rotates the flexed leg laterally — it is the only lateral rotator of the knee and thus has to oppose all medial rotator. Additionally, the long head extends the hip joint. The semitendiosus and the semimembranosus share their origin with the long head of the biceps, and both attaches on the medial side of the proximal head of the tibia together with the gracilis and sartorius to form the pes anserinus. The semitendinosus acts on two joints; extension of the hip, flexion of the knee, and medial rotation of the leg. Distally, the semimembranosus' tendon is divided into three parts referred to as the pes anserinus profondus. Functionally, the semimembranosus is similar to the semitendinosus, and thus produces extension at the hip joint and flexion and medial rotation at the knee.[22] Posteriorly below the knee joint, the popliteus stretches obliquely from the lateral femoral epicondyle down to the posterior surface of the tibia. The subpopliteal bursa is located deep to the muscle. Popliteus flexes the knee joint and medially rotates the leg.[23] Foot Function of foot muscles[24] Movement Muscles (In order of importance) Dorsiflexion • Tibialis anterior • Extensor digitorum longus • Extensor hallucis longus Plantar flexion • Triceps surae • Peroneus longus • Peroneus brevis • Flexor digitorum longus • Tibialis posterior Eversion • Peroneus longus • Peroneus brevis • Extensor digitorum longus • Peroneus tertius Inversion • Triceps surae • Tibialis posterior • Flexor hallucis longus • Flexor digitorum longus • Tibialis anterior With the popliteus (see above) as the single exception, all muscles in the leg are attached to the foot and, based on location, can be classified into an anterior and a posterior group separated from each others by the tibia, the fibula, and the interosseous membrane. In turn, these two groups can be subdivided into subgroups or layers — the anterior Human leg 61 group consists of the extensors and the peroneals, and the posterior group of a superficial and a deep layer. Functionally, the muscles of the leg are either extensors, responsible for the dorsiflexion of the foot, or flexors, responsible for the plantar flexion. These muscles can also classified by innervation, muscles supplied by the anterior subdivision of the plexus and those supplied by the posterior subdivision.[25] The leg muscles acting on the foot are called the extrinsic foot muscles whilst the foot muscles located in the foot are called intrinsic. Dorsiflexion (extension) and plantar flexion occur around the transverse axis running through the ankle joint from the tip of the medial malleolus to the tip of the lateral malleolus. Pronation (eversion) and supination (inversion) occur along the oblique axis of the ankle joint.[24] Extrinsic Three of the anterior muscles are extensors. From its origin on the lateral surface of the tibia and the interosseus mebrane, the three-sided belly of the tibialis anterior extends down below the superior and inferior extensor retinacula to its insertion on the plantar side of the medial cuneiform bone and the fifth metatarsal bone. In the non-weight-bearing leg, the anterior tibialis dorsal flexes the foot and lifts the medial edge of the foot. In the weight-bearing leg, it pulls the leg towards the foot. The extensor digitorum longus has a wide origin stretching from the lateral condyle of the tibia down along the anterior side of the fibula, and the interosseus membrane. At the ankle, the tendon divides into four that stretch across the foot to the dorsal aponeuroses of the last phalanges of the four lateral toes. In the non-weight-bearing leg, the muscle dorsiflexes the digits and the foot, and in the weight-bearing leg acts similar to the tibialis anterior. The extensor hallucis longus has its origin on the fibula and the interosseus membrane between the two other extensors and is, similarly to the extensor digitorum, is inserted on the last phalanx of big toe ("hallux"). The muscle dorsiflexes the hallux, and acts similar to the tibialis anterior in the weight-bearing leg.[26] Two Anterior muscles. muscles on the lateral side of the leg form the peroneal group. The peroneus longus and brevis both have their origins on the fibula and they both pass behind the lateral malleolus where their tendons pass under the peroneal retinacula. Under the foot, the longus stretches from the lateral to the medial side in a groove, thus bracing the transverse arch of the foot. The brevis is attached on the lateral side to the tuberosity of the fifth metatarsal. Together the two peroneals form the strongest pronators of the foot.[27] The peroneus muscles are highly variable and several variants can occasionally be present.[28] Superficial and deep posterior muscles. Of the posterior muscles three are in the superficial layer. The major plantar flexors, commonly referred to as the triceps surae, are the soleus, which arises on the proximal side of both leg bones, and the gastrocnemius, the two heads of which arises on the distal end of the femur. These muscles unite in a large terminal tendon, the Achilles tendon, which is attached to the posterior tubercle of the calcaneus. The plantaris closely follows the lateral head of the gastrocnemius. Its tendon runs between those of the soleus and gastrocnemius and is embedded in the medial end of the calcaneus tendon.[29] Human leg 62 In the deep layer, the tibialis posterior has its origin on the interosseus membrane and the neighbouring bone areas and runs down behind the medial malleolus. Under the foot it splits into a thick medial part attached to the navicular bone and a slightly weaker lateral part inserted to the three cuneiform bones. The muscle produces simultaneous plantar flexion and supination in the non-weight-bearing leg, and approximates the heel to the calf of the leg. The flexor hallucis longus arises distally on the fibula and on the interosseus membrane from where its relatively thick muscle belly extends far distally. Its tendon extends beneath the flexor retinaculum to the sole of the foot and finally attaches on the base of the last phalanx of the hallux. It plantarflexes the hallux and assists in supination. The flexor digitorum longus, finally, has its origin on the upper part of the tibia. Its tendon runs to the sole of the foot where it forks into four terminal tendon attached to the last phalanges of the four lateral toes. It crosses the tendon of the tibialis posterior distally on the tibia, and the tendon of the flexor hallucis longus in the sole. Distally to its division, the quadratus plantae radiates into it and near the middle phalanges its tendons penetrate the tendons of the flexor digitorum brevis. In the non-weight-bearing leg, it plantar flexes the toes and foot and supinates. In the weight-bearing leg it supports the plantar arch.[23] (For the popliteus, see above.) Intrinsic The intrinsic muscles of the foot, muscles whose bellies are located in the foot proper, are either dorsal (top) or plantar (sole). On the dorsal side, two long extrinsic extensor muscles are superficial to the intrinsic muscles, and their tendons form the dorsal aponeurosis of the toes. The short intrinsic extensors and the plantar and dorsal interossei radiates into these aponeuroses. The extensor digitorum brevis and extensor hallucis brevis have a common origin on the anterior side of the calcaneus, from where their tendons extend into the dorsal aponeuroses of digits 1-4. They act to dorsiflex these digits.[30] The plantar muscles can be subdivided into three groups associated with three regions: those of the big digit, the little digit, and the region between these two. All these muscles are covered by the thick and dense plantar aponeurosis, which, together with two tough septa, form the spaces of the three groups. These muscles and their fatty tissue function as cushions that transmit the weight of the body downward. As a whole, the foot is a functional entity.[31] Intrinsic foot muscles The abductor hallucis stretches along the medial edge of the foot, from the calcaneus to the base of the first phalanx of the first digit and the medial sesamoid bone. It is an abductor and a week flexor, and also helps maintain the arch of the foot. Lateral to the abductor hallucis is the flexor hallucis brevis, which originates from the medial cuneiform bone and from the tendon of the tibialis posterior. The flexor hallucis has a medial and a lateral head inserted laterally to the abductor hallucis. It is an important plantar flexor which comes into prominent use in classical ballet (i.e. for pointe work).[31] The adductor hallucis has two heads; a stronger oblique head which arises from the cuboid and lateral cuneiform bones and the bases of the second and third metatarsals; and a transverse head which arises from the distal ends of the third-fifth metatarsals. Both heads are inserted on the lateral sesamoid bone of the first digit. The muscle acts as a tensor to the arches of the foot, but can also adduct the first digit and plantar flex its first phalanx.[32] The opponens digiti minimi originates from the long plantar ligament and the plantar tendinous sheath of peroneus longus and is inserted on the fifth metatarsal. When present, it acts to plantar flex the fifth digit and supports the plantar arch. The flexor digiti minimi arises from the region of base of the fifth metatarsal and is inserted onto the Human leg 63 base of the first phalanx of the fifth digit where it is usually merged with the abductor of the first digit. It acts to plantar flex the last digit. The largest and longest muscles of the little toe is the abductor digiti minimi. Stretching from the lateral process of the calcaneus, with a second attachment on the base of the fifth metatarsal, to the base of the fifth digit's first phalanx, the muscle forms the lateral edge of the sole. Except for supporting the arch, it plantar flexes the little toe and also acts as an abductor.[32] The four lumbricales have their origin on the tendons of the flexor digitorum longus, from where they extend to the medial side of the bases of the first phalanx of digits two-five. Except for reinforcing the plantar arch, they contribute to plantar flexion and move the four digits toward the big toe. They are, in contrast to the lumbricales of the hand, rather variable, sometimes absent and sometimes more than four are present. The quadratus plantae arises with two slips from margins of the plantar surface of the calcaneus and is inserted into the tendon(s) of the flexor digitorum longus, and is known as the "plantar head" of this latter muscle. The three plantar interossei arise with their single heads on the medial side of the third-fifth metatarsals and are inserted on the bases of the first phalanges of these digits. The two heads of the four dorsal interossei arise on two adjacent metatarsals and merge in the intermediary spaces. Their distal attachment is on the bases of the proximal phalanges of the second-fourth digits. The interossei are organized with the second digit as a longitudinal axis; the plantars act as adductors and pull digits 3-5 towards the second digit; while the dorsals act as abductors. Additionally, the interossei act as plantar flexors at the metatarsophalangeal joints. Lastly, the flexor digitorum brevis arises from underneath the calcaneus to insert its tendons on the middle phalanges of digit 2-4. Because the tendons of the flexor digitorum longus run between these tendons, the brevis is sometimes called perforatus. The tendons of these two muscles are surrounded by a tendinous sheath. The brevis acts to plantar flex the middle phalanges.[33] See also: Table of muscles Neurovascular system Arteries The arteries of the leg are divided into a series of segments. In the pelvis area, at the level of the last lumbar vertebra, the abdominal aorta, a continuation the descending aorta, splits into a pair of common iliac arteries. These immediately split into the internal and external iliac arteries, the latter of which descends along the medial border of the psoas major to exits the pelvis area through the vascular lacuna under the inguinal ligament.[34] The artery enters the thigh as the femoral artery which descends the medial side of the thigh to the adductor canal. The canal passes from the anterior to the posterior side of the limb where the artery leaves through the adductor hiatus and becomes the popliteal artery. On the back of the knee the popliteal artery runs through the popliteal fossa to the popliteal muscle where it divides into anterior and posterior tibial arteries.[34] In the lower leg, the anterior tibial enters the extensor compartment near the upper border of the interosseus membrane to descend between the tibialis anterior and the extensor hallucis longus. Distal to the superior and extensor retinacula of the foot it becomes the dorsal artery of the foot. The posterior tibial forms a direct continuation of the popliteal artery which enters the flexor compartment of the lower leg to descend behind the medial malleolus where it divides into the medial and lateral plantar arteries, of which the posterior branch gives rise to the fibular artery.[34] For practical reasons the lower limb is subdivided into somewhat arbitrary regions:[35] The regions of the hip are all located in the thigh: anteriorly, the subinguinal region is bounded by the inguinal ligament, the sartorius, and the pectineus and forms part of the femoral triangle which extends distally to the adductor longus. Posteriorly, the gluteal region corresponds to the gluteus maximus. The anterior region of the thigh extends distally from the femoral triangle to the region of the knee and laterally to the tensor fascia latae. The posterior region ends distally before the popliteal fossa. The anterior and posterior regions of the knee extends from Human leg 64 the proximal regions down to the level of the tuberosity of the tibia. In the lower leg the anterior and posterior regions extends down to the malleoli. Behind the malleoli are the lateral and medial retromalleolar regions and behind these is the region of the heel. Finally, the foot is subdivided into a dorsal region superiorly and a plantar region inferiorly.[35] Veins The veins are subdivided into three systems. The deep or epifascial system returns approximately 85 percent of the blood and the superficial or intermuscular system approximately 15 percent. A series of venous valves called the perforating system interconnects the superficial and deep systems. In the standing posture, the veins of the leg have to handle an exceptional load as they act against gravity when they return the blood to the heart. The venous valves assist in maintaining the superficial-to-deep direction of the blood flow.[36] • • • • • • • Greater saphenous vein Small saphenous Femoral vein Popliteal vein Anterior tibial vein Posterior tibial vein Fibular vein Nerves Nerves of right leg, anterior and posterior aspects The sensory and motor innervation to the lower limb is supplied by the lumbosacral plexus, which is formed by the ventral rami of the lumbar and sacral spinal nerves with additional contributions from the subcostal nerve (T12) and coccygeal nerve (Co1). Based on distribution and topography, the lumbosacral plexus is subdivided into the lumbar plexus (T12-L4) and the Sacral plexus (L5-S4); the latter is often further subdivided into the sciatic and pudendal plexuses:[37] The lumbar plexus is formed lateral to the intervertebral foramina by the ventral rami of the first four lumbar spinal nerves (L1-L4), which all pass through psoas major. The larger branches of the plexus exit the muscle to pass sharply downward to reach the abdominal wall and the thigh (under the inguinal ligament); with the exception of the obturator nerve which pass through the lesser pelvis to reach the medial part of the thigh through the obturator foramen. The nerves of the lumbar plexus pass in front of the hip joint and mainly support the anterior part of the thigh.[37] The iliohypogastric (T12-L1) and ilioinguinal nerves (L1) emerge out of the psoas major near the muscle's origin, from where they run laterally downward to pass anteriorly above the iliac crest between the transversus abdominis and abdominal internal oblique, and then run above the inguinal ligament. Both nerves give off muscular branches to both these muscles. Iliohypogastric supplies sensory branches to the skin of the lateral hip region, and its terminal branch finally pierces the aponeurosis of the abdominal external oblique above the inguinal ring to supply sensory branches to the skin there. Ilioinguinalis exits through the inguinal ring and supplies sensory branches to the skin above the pubic symphysis and the lateral portion of the scrotum.[38] The genitofemoral nerve (L1, L2) leaves Human leg 65 psoas major below the two former nerves, immediately divides into two branches that descends along the muscle's anterior side. The sensory femoral branch supplies the skin below the inguinal ligament, while the mixed genital branch supplies the skin and muscles around the sex organ. The lateral femoral cutaneous nerve (L2, L3) leaves psoas major laterally below the previous nerve, runs obliquely and laterally downward above the iliacus, exits the pelvic area near the iliac spine, and supplies the skin of the anterior thigh.[38] The obturator nerve (L2-L4) passes medially behind psoas major to exit the pelvis through the obturator canal, after which it gives off branches to obturator externus and divides into two branches passing behind and in front of adductor brevis to supply motor innervation to all the other adductor muscles. The anterior branch also supplies sensory nerves to the skin on a small area on the distal medial aspect of the thigh.[39] The femoral nerve (L2-L4) is the largest and longest of the nerves of the lumbar plexus. It supplies motor innervation to iliopsoas, pectineus, sartorius, and quadriceps; and sensory branches to the anterior thigh, medial lower leg, and posterior foot.[39] The nerves of the sacral plexus pass behind the hip joint to innervate the posterior part of the thigh, most of the lower leg, and the foot.[37] The superior (L4-S1) and inferior gluteal nerves (L5-S2) innervate the gluteus muscles and the tensor fascia latae. The posterior femoral cutaneous nerve (S1-S3) contributes sensory branches to the skin on the posterior thigh.[40] The sciatic nerve (L4-S3), the largest and longest nerve in the human body, leaves the pelvis through the greater sciatic foramen. In the posterior thigh if first gives off branches to the short head of the biceps femoris and then divides into the tibial (L4-S3) and common fibular nerves (L4-S2). The fibular nerve continues down on the medial side of biceps femoris, winds around the fibular neck and enters the front of the lower leg. There it divides into a deep and a superficial terminal branch. The superficial branch supplies the peroneus muscles and the deep branch enters the extensor compartment; both branches reaches into the dorsal foot. In the thigh, the tibial nerve gives off branches to semitendinosus, semimembranosus, adductor magnus, and the long head of the biceps femoris. The nerve then runs straight down the back of the leg, through the popliteal fossa to supply the ankle flexors on the back of the lower leg and then continues down to supply all the muscles in the sole of the foot.[41] The pudendal (S2-S4) and coccygeal nerves (S5-Co2) supply the muscles of the pelvic floor and the surrounding skin.[42] The picture on the top shows a woman's legs and the below picture a young male's legs in long shorts The lumbosacral trunk is a communicating branch passing between the sacral and lumbar plexuses containing ventral fibers from L4. The coccygeal nerve, the last spinal nerve, emerges from the sacral hiatus, unites with the ventral rami of the two last sacral nerves, and forms the coccygeal plexus.[37] Human leg Fracture A fracture of the leg (called "broken leg") can be classified according to the involved bone into: • Femoral fracture (in the upper leg) • Crus fracture (in the lower leg) A crus fracture, in turn, can involve only the tibia (tibial fracture), only the fibula (fibular fracture) or both. Cultural aspects Adolescent and adult women in many Western cultures often remove the hair from their legs. Toned, tanned, shaved legs are sometimes perceived as a sign of youthfulness and are often considered attractive in these cultures. Men generally do not shave their legs in any culture. However, leg-shaving is a generally accepted practice in modeling. It is also fairly common in sports where the hair removal makes the athlete appreciably faster by reducing drag; the most common case of this is competitive swimming. It is also practised in many other sports, in which skin injuries are common: the absence of grown hair makes nicks, scratches and bruises heal faster because of the reduced microbial population on shaved skin. Legs are often used metaphorically in many cultures to indicate either strength or mobility. The supporting columns of an object may be referred to as legs as well, as in chair legs. Notes [1] http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2011/ MB_cgi?mode=& term=Leg [2] http:/ / www. mercksource. com/ pp/ us/ cns/ cns_hl_dorlands_split. jsp?pg=/ ppdocs/ us/ common/ dorlands/ dorland/ five/ 000058188. htm [3] "Lower Extremity" (http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2007/ MB_cgi?mode=& term=Lower+ Extremity& field=entry). Medical Subject Headings (MeSH). National Library of Medicine. . Retrieved 2009-04-18. [4] "lower limb" (http:/ / www. mercksource. com/ pp/ us/ cns/ cns_hl_dorlands_split. jsp?pg=/ ppdocs/ us/ common/ dorlands/ dorland/ five/ 000060202. htm#000060202). Dorland's Medical Dictionary for Healthcare Consumers. Elsevier. . Retrieved 2009-04-18. [5] "Leg" (http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2007/ MB_cgi?mode=& term=Leg& field=entry). Medical Subject Headings (MeSH). National Library of Medicine. . Retrieved 2009-04-18. [6] "leg" (http:/ / www. mercksource. com/ pp/ us/ cns/ cns_hl_dorlands_split. jsp?pg=/ ppdocs/ us/ common/ dorlands/ dorland/ five/ 000058188. htm). Dorland's Medical Dictionary for Healthcare Consumers. Elsevier. . Retrieved 2009-04-18. [7] Merriam-Webster Dictionary leg (http:/ / www. m-w. com/ dictionary/ leg) [8] leg (http:/ / www. emedicinehealth. com/ script/ main/ srchcont_dict. asp?src=leg) at eMedicine Dictionary [9] Thieme Atlas of Anatomy (2006), p 360 [10] Thieme Atlas of Anatomy (2006), p 361 [11] Thieme Atlas of Anatomy (2006), p 362 [12] Platzer (2004), p 196 [13] Platzer (2004), pp 244-247 [14] Platzer, (2004), p 232 [15] Platzer (2004), p 234 [16] Platzer (2004), p 236 [17] Platzer (2004), p 238 [18] Platzer (2004), p 240 [19] Platzer (2004), p 242 [20] Platzer (2004), p 252 [21] Platzer (2004), p 248 [22] Platzer (2004), p 250 [23] Platzer (2004), p 264 [24] Platzer (2004), p 266 [25] Platzer (2004), p 256 [26] Platzer (2004), p 258 [27] Platzer (2004), p 260 [28] Chaitow (2000), p 554 [29] Platzer (2004), p 262 [30] Platzer (2004), p 268 66 Human leg [31] [32] [33] [34] Platzer (2004), p 270 Platzer (2004), p 272 Platzer (2004), p 274 Thieme Atlas of Anatomy (2006), p 464 [35] [36] [37] [38] [39] [40] [41] [42] Platzer (2004), p 412 Thieme Atlas of Anatomy (2006), pp 466-467 Thieme Atlas of anatomy (2006), pp 470-471 Thieme Atlas of anatomy (2006), pp 472-473 Thieme Atlas of anatomy (2006), pp 474-475 Thieme Atlas of Anatomy (2006), p 476 Thieme Atlas of Anatomy (2006), pp 480-481 Thieme Atlas of Anatomy (2006), pp 482-483 References • Chaitow, Leon; Walker DeLany, Judith (2000). Clinical Application of Neuromuscular Techniques: The Lower Body (http://books.google.com/?id=09fssXGvlrIC&pg=PA554). Elsevier Health Sciences. ISBN 0443062846. • consulting editors, Lawrence M. Ross, Edward D. Lamperti; authors, Michael Schuenke, Erik Schulte, Udo Schumacher. (2006). Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. ISBN 1-58890-419-9. • Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. ISBN 3-13-533305-1. External links • Interactive Rotation of Leg Arteries and Veins (http://www.landholt.com/Interactive/Rotation_AV) 67 Knee 68 Knee Knee Right knee Latin articulatio genus Gray's subject #93 339 Nerve femoral, obturator, sciatic MeSH Knee [1] [2] Dorlands/Elsevier Knee [3] The knee joint joins the thigh with the leg and consists of two articulations: one between the femur and tibia, and [4] [5] one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is [6] a mobile trocho-ginglymus (i.e. a pivotal hinge joint), which permits flexion and extension as well as a slight medial and lateral rotation. Since in humans the knee supports nearly the whole weight of the body, it is vulnerable to both acute injury and the development of osteoarthritis. It is often grouped into tibiofemoral and patellofemoral components.[7] considered with tibiofemoral components.)[9] [8] (The fibular collateral ligament is often Human anatomy The knee is a complex, compound, condyloid variety of a synovial joint. It actually comprises three functional compartments: the femoropatellar articulation consists of the patella, or "kneecap", and the patellar groove on the front of the femur through which it slides; and the medial and lateral femorotibial articulations linking the femur, or thigh bone, with the tibia, the main bone of the lower leg.[10] The joint is bathed in synovial fluid which is contained inside the synovial membrane called the joint capsule. Articular surfaces of femur. Upon birth, a baby will not have a conventional knee cap, but a growth formed of cartilage. In females this turns to a normal bone knee cap by the age of 3, in males the age of 5. Knee 69 Articular bodies The articular bodies of the femur are its lateral and medial condyles. These diverge slightly distally and posteriorly, with the lateral condyle being wider in front than at the back while the medial condyle is of more constant width.[11] The radius of the condyles' curvature in the sagittal plane becomes smaller toward the back. This diminishing radius produces a series of involute midpoints (i.e. located on a spiral). The resulting series of transverse axes permit the sliding and rolling motion in the flexing knee while ensuring the collateral ligaments are sufficiently lax to permit the rotation associated with the curvature of the medial condyle about a vertical axis.[12] Articular surfaces of tibia. The pair of tibial condyles are separated by the intercondylar eminence[11] composed of a lateral and a medial [13] tubercle. The patella is inserted into the thin anterior wall of the joint capsule.[11] On its posterior surface is a lateral and a medial articular surface,[12] both of which communicate with the patellar surface which unites the two femoral condyles on the anterior side of the bone's distal end.[14] A common disease found in the knee is "Tartas". Articular capsule Lateral and posterior aspects of right knee The articular capsule has a synovial and a fibrous membrane separated by fatty deposits. Anteriorly, the synovial membrane is attached on the margin of the cartilage both on the femur and the tibia, but on the femur, the [15] The suprapatellar bursa is prevented from being suprapatellar bursa or recess extends the joint space proximally. [16] pinched during extension by the articularis genu muscle. Behind, the synovial membrane is attached to the margins of the two femoral condyles which produces two extensions similar to the anterior recess. Between these two extensions, the synovial membrane passes in front of the two cruciate ligaments at the center of the joint, thus forming a pocket direct inward.[15] Bursae Numerous bursae surround the knee joint. The largest communicative bursa is the suprapatellar bursa described above. Four considerably smaller bursae are located on the back of the knee. Two non-communicative bursae are located in front of the patella and below the patellar tendon, and others are sometimes present. [15] Cartilage Cartilage is a thin, elastic tissue that protects the bone and makes certain that the joint surfaces can slide easily over each other. Cartilage ensures supple knee movement. There are two types of joint cartilage in the knees: fibrous cartilage (the meniscus) and hyaline cartilage. Fibrous cartilage has tensile strength and can resist pressure. Hyaline cartilage covers the surface along which the joints move. Cartilage will wear over the years. Cartilage has a very Knee 70 limited capacity for self-restoration. The newly formed tissue will generally consist for a large part of fibrous cartilage of lesser quality than the original hyaline cartilage. As a result, new cracks and tears will form in the cartilage over time. Menisci The articular disks of the knee-joint are called menisci because they only partly divide the joint space.[17] These two disks, the medial meniscus and the lateral meniscus, consist of connective tissue with extensive collagen fibers containing cartilage-like cells. Strong fibers run along the menisci from one attachment to the other, while weaker radial fibers are interlaced with the former. The menisci are flattened at the center of the knee joint, fused with the synovial membrane laterally, and can move over the tibial surface. [18] The menisci serve to protect the ends of the bones from rubbing on each other and to effectively deepen the tibial sockets into which the femur attaches. They also play a role in shock absorption, and may be cracked, or torn, when the knee is forcefully rotated and/or bent. Ligaments The ligaments surrounding the knee joint offer stability by limiting movements and, together with several menisci and bursae, protect the articular capsule. Intracapsular The knee is stabilized by a pair of cruciate ligaments. The anterior cruciate ligament (ACL) stretches from the lateral condyle of femur to the anterior intercondylar area. The ACL is critically important because it prevents the tibia from being pushed too far anterior relative to the femur. It is often torn during twisting or bending of the knee. The posterior cruciate ligament (PCL) stretches from medial condyle of femur to the posterior intercondylar area. Injury to this ligament is uncommon but can occur as a direct result of forced trauma to the ligament. This ligament prevents posterior displacement of the tibia relative to the femur. The transverse ligament stretches from the lateral meniscus to the medial meniscus. It passes in front of the menisci. Is divided into several strips in 10% of cases.[18] The two menisci are attached to each others anteriorly by the ligament.[19] The posterior and anterior meniscofemoral ligaments stretch from posterior horn of lateral meniscus to the medial femoral condyle. They pass posteriorly behind the posterior cruciate ligament. The posterior meniscofemoral ligament is more commonly present (30%); both ligaments are present less often.[18] The meniscotibial ligaments (or "coronary") stretches from inferior edges of the mensici to the periphery of the tibial plateaus. Anterolateral aspect of right knee. Anteromedial aspect of knee Extracapsular The patellar ligament connects the patella to the tuberosity of the tibia. It is also occasionally called the patellar tendon because there is no definite separation between the quadriceps tendon (which surrounds the patella) and the Knee 71 area connecting the patella to the tibia.[20] This very strong ligament helps give the patella its mechanical leverage[21] and also functions as a cap for the condyles of the femur. Laterally and medially to the patellar ligament the lateral and medial patellar retinacula connect fibers from the vasti lateralis and medialis muscles to the tibia. Some fibers from the iliotibial tract radiate into the lateral retinaculum and the medial retinaculum receives some transverse fibers arising on the medial femoral epicondyle. [11] The medial collateral ligament (MCL a.k.a. "tibial") stretches from the medial epicondyle of the femur to the medial tibial condyle. It is composed of three groups of fibers, one stretching between the two bones, and two fused with the medial meniscus. The MCL is partly covered by the pes anserinus and the tendon of the semimembranosus passes under it.[11] It protects the medial side of the knee from being bent open by a stress applied to the lateral side of the knee (a valgus force). The lateral collateral ligament (LCL a.k.a. "fibular") stretches from the lateral epicondyle of the femur to the head of fibula. It is separate from both the joint capsule and the lateral meniscus.[11] It protects the lateral side from an inside bending force (a varus force). Lastly, there are two ligaments on the dorsal side of the knee. The oblique popliteal ligament is a radiation of the tendon of the semimembranosus on the medial side, from where it is direct laterally and proximally. The arcuate popliteal ligament originates on the apex of the head of the fibula to stretch proximally, crosses the tendon of the popliteus muscle, and passes into the capsule.[11] Movements Maximum movements[22] and muscles[23] Extension 5-10° Flexion 120-150° (In order of importance) Quadriceps (with Semimembranosus some assistance from the Tensor fasciae latae) Semitendinosus Biceps femoris Gracilis Sartorius Popliteus Gastrocnemius Internal rotation* 10° External rotation* 30-40° (In order of importance) Biceps femoris Semimembranosus Semitendinosus Gracilis Sartorius Popliteus *(knee flexed 90°) The knee permits flexion and extension about a virtual transverse axis, as well as a slight medial and lateral rotation about the axis of the lower leg in the flexed position. The knee joint is called "mobile" because the femur and lateral meniscus move[24] over the tibia during rotation, while the femur rolls and glides over both menisci during extension-flexion.[25] The center of the transverse axis of the extension/flexion movements is located where both collateral ligaments and both cruciate ligaments intersect. This center moves upward and backward during flexion, while the distance between the center and the articular surfaces of the femur changes dynamically with the decreasing curvature of the femoral condyles. The total range of motion is dependent on several parameters such as soft-tissue restraints, active insufficiency, and hamstring tightness.[22] Knee 72 Extended position With the knee extended both the lateral and medial collateral ligaments, as well as the anterior part of the anterior cruciate ligament, are taut. During extension, the femoral condyles glide into a position which causes the complete unfolding of the tibial collateral ligament. During the last 10° of extension, an obligatory terminal rotation is triggered in which the knee is rotated medially 5°. The final rotation is produced by a lateral rotation of the tibia in the non-weight-bearing leg, and by a medial rotation of the femur in the weight-bearing leg. This terminal rotation is made possible by the shape of the medial femoral condyle, assisted by contraction of the popliteus muscle and the iliotibial tract and is caused by the stretching of the anterior cruciate ligament. Both cruciate ligaments are slightly unwinded and both lateral ligaments become taut.[25] Flexed position In the flexed position, the collateral ligaments are relaxed while the cruciate ligaments are taut. Rotation is controlled by the twisted cruciate ligaments; the two ligaments get twisted around each other during medial rotation of the tibia — which reduces the amount of rotation possible — while they become unwounded during lateral rotation of the tibia. Because of the oblique position of the cruciate ligaments at least a part of one of them is always tense and these ligaments control the joint as the collateral ligaments are relaxed. Furthermore, the dorsal fibers of the tibial collateral ligament become tensed during extreme medial rotation and the ligament also reduces the lateral rotation to 45-60°.[25] Blood supply The femoral artery and the popliteal artery help form the arterial network surrounding the knee joint (articular rete). There are 6 main branches: • 1. Superior medial genicular artery • 2. Superior lateral genicular artery • 3. Inferior medial genicular artery • 4. Inferior lateral genicular artery • 5. Descending genicular artery • 6. Recurrent branch of anterior tibial artery The medial genicular arteries penetrate the knee joint. Arteries of the knee Disorders and injury Knee pain is caused by trauma, misalignment, and degeneration as well as by conditions like arthritis.[26] The most common knee disorder is generally known as patellofemoral syndrome.The majority of minor cases of knee pain can be treated at home with rest and ice but more serious injuries do require surgical care.[27] One form of patellofemoral syndrome involves a tissue-related problem that creates pressure and irritation in the knee between the patella and the trochlea (patellar compression syndrome), which causes pain. The second major class of knee disorder involves a tear, slippage, or dislocation that impairs the structural ability of the knee to balance the leg (patellofemoral instability syndrome). Patellofemoral instability syndrome may cause either pain, a sense of poor balance, or both.[28] Age also contributes to disorders of the knee. Particularly in older people, knee pain frequently arises due to osteoarthritis. In addition, weakening of tissues around the knee may contribute to the problem.[29] Patellofemoral instability may relate to hip abnormalities or to tightness of surrounding ligaments.[28] Knee 73 Cartilage lesions can be caused by: • • • • • • Accidents (fractures) Injuries The removal of a meniscus Anterior cruciate ligament injury Posterior cruciate ligament injury Considerable strain on the knee. Any kind of work during which the knees undergo heavy stress may also be detrimental to cartilage. This is especially the case in professions in which people frequently have to walk, lift, or squat. Other causes of pain may be excessive on, and wear of, the knees, in combination with such things as muscle weakness and overweight. Common complaints: • A painful, blocked, locked or swollen knee. • Sufferers sometimes feel as if their knees are about to give way, or may feel uncertain about their movement. The pain felt by people with cartilage injury does not come from the cartilage itself, but from the irritated tissue surrounding the cartilage, or from pieces of cartilage that have come loose. If cartilage injury goes untreated, the layer of cartilage will continue to gradually wear away, causing arthrosis and gradual immobility. Overall fitness and knee injury Physical fitness is related integrally to the development of knee problems. The same activity such as climbing stairs may cause pain from patellofemoral compression for someone who is physically unfit, but not for someone else (or even for that person at a different time). Obesity is another major contributor to knee pain. For instance, a 30-year-old woman who weighed 120 lb at age 18 years, before her three pregnancies, and now weighs 285 lb, had added 660 lb of force across her patellofemoral joint with each step.[30] Common injuries due to physical activity In sports that place great pressure on the knees, especially with twisting forces, it is common to tear one or more ligaments or cartilages. Anterior cruciate ligament injury ACL is the most commonly injured ligament of the knee. The injury is common during sports. Twisting of the knee is a common cause of over-stretching or tearing the ACL. When the ACL is injured one may hear a popping sound and the leg may suddenly give out. Besides swelling and pain, walking may be painful and the knee will feel unstable. Minor tears of the anterior cruciate ligament may heal over time, but a torn ACL requires surgery. After surgery, recovery is prolonged and low impact exercises are recommended to strengthen the joint.[31] Model demonstrating parts of an artificial knee Torn meniscus injury Knee 74 The menisci act as shock absorbers and separate the two ends of bone in the knee joint. There are two menisci in the knee, the medial (inner) and the lateral (outer). When there is torn cartilage, it means that the meniscus has been injured. Meniscus tears occur during sports often when the knee is twisted. Menisci injury may be innocuous and one may be able to walk after a tear, but soon swelling and pain set in. Sometimes the knee will lock while bending. Pain often occurs when one squats. Small meniscus tears are treated conservatively but most large tears require surgery.[32] Fractures Knee fractures are rare but do occur, especially as a result of motor vehicle accidents. There is usually immediate pain; swelling and one may not be able to stand on the leg. The muscles go into spasm and even the slightest movements are painful. X-rays can easily confirm the injury and surgery depends on the degree of displacement and type of fracture. Ruptured tendon Tendons usually attach muscle to bone. In the knee the quadriceps and patellar tendon can sometimes tear. The injuries to these tendons occur when there is forceful contraction of the knee. If the tendon is completely torn, bending or extending the leg is impossible. A completely torn tendon requires surgery but a partially torn tendon can be treated with leg immobilization followed by physical therapy. Overuse Overuse injuries of the knee include tendonitis, bursitis, muscle strains and iliotibial band syndrome. These injuries often develop slowly over weeks or months. Activities that induce pain usually delay healing. Rest, ice and compression do help in most cases. Once the swelling has diminished, heat packs can increase blood supply and promote healing. Most overuse injuries subside with time but can flare up if the activities are quickly resumed.[33] To prevent overuse injuries, warm up prior to exercise, limit high impact activities and keep your weight under control. Surgical interventions Before the advent of arthroscopy and arthroscopic surgery, patients having surgery for a torn ACL required at least nine months of rehabilitation, having initially spent several weeks in a full-length plaster cast. With current techniques, such patients may be walking without crutches in two weeks, and playing some sports in a few months. In addition to developing new surgical procedures, ongoing research is looking into underlying problems which may increase the likelihood of an athlete suffering a severe knee injury. These findings may lead to effective preventive measures, especially in female athletes, who have been shown to be especially vulnerable to ACL tears from relatively minor trauma. Articular cartilage repair treatment : • • • • • Arthroscopic debriment of the knee (arthroscopic lavage). Mosaïc-plasty. Microfracture (Ice-picking). Autologous Chondrocyte Implantation. Osteochondral Autograft and Allografts. Knee 75 Diagnostics The ideal diagnostic test for assessing knee pain are the standard AP and lateral views of plain x-rays as a person in knee pain may not be able to stand. Magnetic resonance imaging is often used for diagnosing soft tissue injuries of the knee. But sometimes it can be overly sensitive; and can even detect tears and signs of inflammation in people who have no pain in their knees. Arthroscopy may be used to examine the knee as well as perform surgical tasks like removal of free fragments and repair of meniscal and ligament injuries. Several diagnostic maneuvers help clinicians diagnose an injured ACL. In the anterior drawer test, the examiner applies an anterior force on the proximal tibia with the knee in 90 degrees of flexion. The Lachman test is similar, but performed with the knee in only about twenty degrees of flexion, which is more comfortable to a patient in acute pain. The pivot-shift test adds a valgus (outside-in) force to the knee while it is moved from flexion to extension. Any abnormal motion in these maneuvers, suggests a tear of the collateral or cruciate ligaments of the knee. The diagnosis of soft tissue injuries is usually confirmed by MRI, while that of bone injuries by a CT Scan. The availability of sophisticated investigations, like CT Scan with 3D reconstruction, has greatly decreased the number of purely diagnostic arthroscopies performed. Animal anatomy In humans the knee refers to the joints between the femur, tibia and patella. In quadrupeds, particularly horses and ungulates the term is commonly used to refer to the carpus, probably because of its similar hinge or ginglymus action. The joints between the femur, tibia and patella are known as the stifle in quadrupeds. In insects and other animals the term knee is used widely to refer to any ginglymus joint. Additional images Knee MR Knee 76 Knee MR Knee X-ray Knee 77 Cruciate ligaments Left knee-joint from behind, showing interior ligaments. Knee 78 Capsule of right knee-joint (distended). Lateral aspect. Anterior and lateral view of knee. Notes [1] http:/ / education. yahoo. com/ reference/ gray/ subjects/ subject?id=93#p339 [2] [3] [4] [5] [6] [7] http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2011/ MB_cgi?mode=& term=Knee http:/ / www. mercksource. com/ pp/ us/ cns/ cns_hl_dorlands_split. jsp?pg=/ ppdocs/ us/ common/ dorlands/ dorland/ five/ 000056558. htm knee+joint (http:/ / www. emedicinehealth. com/ script/ main/ srchcont_dict. asp?src=knee+ joint) at eMedicine Dictionary Kulowski (1932), p 618 See trochoid and ginglymus. Rytter S, Egund N, Jensen LK, Bonde JP (2009). "Occupational kneeling and radiographic tibiofemoral and patellofemoral osteoarthritis" (http:/ / www. occup-med. com/ content/ 4/ / 19). J Occup Med Toxicol 4: 19. doi:10.1186/1745-6673-4-19. PMC 2726153. PMID 19594940. . [8] Gill TJ, Van de Velde SK, Wing DW, Oh LS, Hosseini A, Li G (December 2009). "Tibiofemoral and patellofemoral kinematics after reconstruction of an isolated posterior cruciate ligament injury: in vivo analysis during lunge" (http:/ / ajs. sagepub. com/ cgi/ pmidlookup?view=long& pmid=19726621). Am J Sports Med 37 (12): 2377–85. doi:10.1177/0363546509341829. PMID 19726621. . [9] Scott J, Lee H, Barsoum W, van den Bogert AJ (November 2007). "The effect of tibiofemoral loading on proximal tibiofibular joint motion" (http:/ / www3. interscience. wiley. com/ resolve/ openurl?genre=article& sid=nlm:pubmed& issn=0021-8782& date=2007& volume=211& issue=5& spage=647). J. Anat. 211 (5): 647–53. doi:10.1111/j.1469-7580.2007.00803.x. PMC 2375777. PMID 17764523. . [10] Burgener (2002), p 390 [11] Platzer (2004), p 206 [12] Platzer (2004), pp 194-195 [13] Platzer (2004), p 202 [14] Platzer (2004), p 192 [15] Platzer (2004), p 210 Knee [16] B Reider, JL Marshall, B Koslin, B Ring and FG Girgis (1981). "The anterior aspect of the knee joint" (http:/ / www. ejbjs. org/ cgi/ reprint/ 63/ 3/ 351. pdf). J Bone Joint Surg Am. 1981;63:351-356.. . Retrieved 2010-08-17. [17] Platzer (2004), p 26 [18] Platzer (2004), p 208 [19] Diab (1999), p 200 [20] MedicineNet.com, Definition of Patellar tendon [21] Moore (2006), p 194 [22] Thieme Atlas of Anatomy (2006), pp 398-399 [23] Platzer (2004), p 252 [24] Thieme Atlas of Anatomy (2006), p 399 [25] Platzer (2004), pp 212-213 [26] " Back of Knee Pain Causes (http:/ / healthlifeandstuff. com/ 2009/ 07/ back-of-knee-pain-causes/ ) [27] Knee anatomy facts and myths (http:/ / www. kneeanatomy. net/ ) 2010-01-26 [28] Afra R and Schepsis A (May 28, 2008). "Addressing patellofemoral pathology: Biomechanics and classification" (http:/ / jmm. consultantlive. com/ article/ 1145622/ 1403741). The Journal of Musculoskeletal Medicine. . [29] Pill SG, Khoury LD, Chin GC et al. (October 29, 2008). "MRI for evaluating knee pain in older patients: How useful is it?" (http:/ / jmm. consultantlive. com/ display/ article/ 1145622/ 1404837). The Journal of Musculoskeletal Medicine. . [30] Andrish JT (May 8, 2009). "Sports injuries in weekend warriors: 20 Clinical pearls" (http:/ / jmm. consultantlive. com/ display/ article/ 1145622/ 1412245). The Journal of Musculoskeletal Medicine 26 (5). . [31] Knee pain and injuries (http:/ / sportsmedicine. about. com/ od/ kneepainandinjuries/ Knee_Pain_and_Injuries. htm) About sports online portal. 2010-01-26 [32] Tandeter, Howard B. "Acute Knee Injuries: Use of Decision Rules for Selective Radiograph Ordering" (http:/ / www. aafp. org/ afp/ 991201ap/ 2599. html) 2010-01-26. [33] Knee injuries and disorders (http:/ / www. nlm. nih. gov/ medlineplus/ kneeinjuriesanddisorders. html) MedLine Plus. 2010-01-26 References • Burgener, Francis A.; Meyers, Steven P.; Tan, Raymond K. (2002). Differential Diagnosis in Magnetic Resonance Imaging (http://books.google.com/?id=brsH_IqPzzoC&pg=PA390). Thieme. ISBN 1588900851. • Diab, Mohammad (1999). Lexicon of Orthopaedic Etymology (http://books.google.com/?id=fstFQVnw8-wC& pg=PA200). Taylor & Francis. ISBN 9057025973. • Kulowski, Jacob (1932). Flexion Contracture of the Knee: The Mechanics of the Muscular Contracture and the Turnbuckle Cast Method of Treatment (http://www.ejbjs.org/cgi/reprint/14/3/618.pdf). Journal of Bone and Joint Surgery. • Moore, Keith L.; Dalley, Arthur F.: Agur, A. M. R. (2006). Clinically Oriented Anatomy (http://books.google. com/?id=SxuA3T7JbQkC&pg=PA594). Lippincott Williams & Wilkins. ISBN 0781736390. • Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. pp. 206–213. ISBN 3-13-533305-1. • "Definition of patellar tendon" (http://www.medterms.com/script/main/art.asp?articlekey=34200). MedicineNet.com. Retrieved 2008-12-11. • Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. 2006. ISBN 1-58890-419-9. 79 Ladle (spoon) 80 Ladle (spoon) A ladle is a type of spoon used to scoop up and serve soup, lasagne, or other foods. Although designs vary, a typical ladle has a long handle terminating in a deep bowl, frequently with the bowl oriented at an angle to the handle to facilitate lifting liquid out of a pot or other vessel and conveying it to a bowl. Some ladles involve a point on the side of the basin to allow for finer stream when pouring the liquid; however, this can create difficulty for left handed users, as it is easier to pour towards one's self. Thus, many of these ladles feature such pinches on both sides. Ladles are usually made of the same stainless steel alloys as other kitchen utensils; however, they can be made of aluminium, silver, plastics, melamine resin, wood, bamboo or other materials. Ladles are made in a variety of sizes, the larger ones being about 1 foot (30 cm) in length, with the different sizes tailored to the intended use. Sterling silver ladle - hallmarked London silver 1876-7 (on 5cm squares) Aluminium ladle (on 5cm squares) Melamine ladle (on 5cm squares) Stainless steel ladle (on 5cm squares) Ladle (spoon) 81 Copper alloy ladle Meat slicer A meat slicer, also called a slicing machine, deli slicer or simply a slicer, is a tool used in butcher shops and delicatessens to slice meats and cheeses. The first meat slicer was invented by Wilhelm van Berkel in Rotterdam in 1898.[1] [2] [3] Older models of meat slicer may be operated by crank, while newer ones generally use an electric motor.[4] More recently, meat slicers have become available in the home market for people wanting to slice their own meats and cheeses.[5] References [1] Feith, Jan (1922). Modern Holland. Nijgh & van Ditmar's Publishing Co.,ltd. pp. 245. Antique meat slicer. [2] "Berkel" (http:/ / www. averyberkel. com/ main. aspx?p=1. 1. 3. 7). Avery Berkel. . Retrieved 2008-10-05. [3] "Company history" (http:/ / www. berkelcompany. com/ details. cfm?id=61). Berkel. . Retrieved 2008-10-05. [4] "Vintage Hand-cranked Meat Slicers Popular Among ‘Green’ Chefs and Restaurants" (http:/ / www. emiliomiti. com/ restaurant-news/ vintage-hand-cranked-meat-slicers-popular-among-green-chefs-and-restaurants/ ). Emiliomiti LLC. . Retrieved 2008-10-05. [5] Chu, Louisa. "Ultimate Boy Toy Meat slicers come out from behind the butcher counter" (http:/ / www. chow. com/ stories/ 10197). Chow. . Retrieved 2008-10-05. Nail (anatomy) 82 Nail (anatomy) Fingernails Toenails A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws, which are found on numerous other animals. Fingernails and toenails are made of a tough protein called keratin, as are animals' hooves and horns. The mammalian nail, claw, and hoof are all examples of unguis [plural ungues]. Human anatomy The nail consists of the nail plate, the nail matrix and the nail bed below it, and the grooves surrounding it.[1] Parts of the nail Nail Basic nail anatomy Latin unguis Code TH H3.12.00.3.02001 The matrix (synonyms:[2] matrix unguis, keratogenous membrane, nail matrix, onychostroma) is the tissue (or germinal matrix) upon which the nail rests,[3] the part of the nail bed that extends beneath the nail root and contains nerves, lymph and blood vessels.[4] The matrix is responsible for the production of the cells that become the nail plate. The width and thickness of the nail plate is determined by the size, length, and thickness of the matrix, while the shape of the fingertip itself determines if the nail plate is flat, arched, or hooked.[5] The matrix will continue to grow as long as it receives nutrition and remains in a healthy condition.[4] As new nail plate cells are incubated, they emerge from the matrix round and white to push older nail plate cells forward; and in this way yet older cells become compressed, flat, and translucent, making the pink colour of the capillaries in the nail bed below visible.[6] The lunula (occasionally called simply "the moon") is the visible part of the matrix, the whitish crescent-shaped base [7] of the visible nail. The lunula is largest in the thumb and often absent in the little finger. Nail (anatomy) The nail bed is the skin beneath the nail plate.[7] Like all skin, it is composed of two types of tissues: the deeper dermis, the living tissue fixed to the bone which contains capillaries and glands,[8] and the superficial epidermis, the layer just beneath the nail plate which moves forward with the plate. The epidermis is attached to the dermis by tiny longitudinal "grooves"[5] known as the matrix crests or crests of nail matrix (cristae matricis unguis).[3] [8] As we age, the plate grows thinner and these ridges become evident in the plate itself.[5] The nail sinus (sinus unguis) is the deep furrow into which the nail root is inserted.[3] The nail root (radix unguis) is the part of nail situated in the nail sinus,[3] i.e. the base of the nail embedded underneath the skin. It originates from the actively growing tissue below, the matrix.[4] The nail plate or body of nail (corpus unguis)[3] is the actual nail, and like hair and skin, made of translucent keratin protein made of amino acids. In the nail it forms a strong flexible material made of several layers of dead, flattened cells.[5] The plate appears pink because of the underlying capillaries.[7] Its (transversal) shape is determined by the form of the underlying bone.[5] In common usage, the word nail often refers to the this part only. The free margin (margo liber) or distal edge is the anterior margin of the nail plate corresponding to the abrasive or cutting edge of the nail.[3] The hyponychium (informally known as the "quick")[9] is the epithelium located beneath the nail plate at the junction between the free edge and the skin of the fingertip. It forms a seal that protects the nail bed.[4] The onychodermal band is the seal between the nail plate and the hyponychium. It is found just under the free edge, in that portion of the nail where the nail bed ends and can be recognized by its glassy, greyish colour (in fair-skinned people). It is not perceptible in some individuals while it is highly prominent on others.[5] The eponychium is the small band of epithelium that extends from the posterior nail wall onto the base of the nail.[3] Often and erroneously called the "proximal fold" or "cuticle", the eponychium is the end of the proximal fold that folds back upon itself to shed an epidermal layer of skin onto the newly formed nail plate. This layer of non-living, almost invisible skin is the cuticle that "rides out" on the surface of the nail plate. Together, the eponychium and the cuticle form a protective seal. The cuticle on the nail plate is dead cells and is often removed during manicure, but the eponychium is living cells and should not be touched.[6] The perionyx is the projecting edge of the eponychium covering the proximal strip of the lunula.[3] The nail wall (vallum unguis) is the cutaneous fold overlapping the sides and proximal end of the nail. The lateral margin (margo lateralis) is lying beneath the nail wall on the sides of the nail and the nail groove or fold (sulcus matricis unguis) are the cutaneous slits into which the lateral margins are embedded.[3] The paronychium is the border tissue around the nail[10] and paronychia is an infection in this area. Function Aesthetics aside, a healthy (finger)nail has the function of protecting the distal phalanx, the fingertip, and the surrounding soft tissues from injuries. It also serves to enhance precise delicate movements of the distal digits through counter-pressure exerted on the pulp of the finger. [1] The nail then acts as a counterforce when the end of the finger touches an object, thereby enhancing the sensitivity of the fingertip,[11] even though there are no nerve endings in the nail itself. Finally, the nail functions as a tool, enabling for instance a so called "extended precision grip" (e.g. pulling out a splinter in one's finger). 83 Nail (anatomy) 84 Growth The growing part of the nail is the part still under the skin at the nail's proximal end under the epidermis, which is the only living part of a nail. In mammals, the length and growth rate of nails is related to the length of the terminal phalanges (outermost finger bones). Thus, in humans, the nail of the index finger grows faster than that of the little finger; and fingernails grow up to four times faster than toenails. [12] In humans, nails grow at an average rate of 3 mm (0.12 in) a month (as they are a form of hair).[13] Fingernails require 3 to 6 months to regrow completely, and toenails require 12 to 18 months. Actual growth rate is dependent upon age, gender, season, exercise level, diet, and hereditary factors. Nails grow faster in the summer than in any other season.[14] Contrary to popular belief, nails do not continue to grow after death; the skin dehydrates and tightens, making the nails (and hair) appear to grow.[15] Medical aspects Healthcare and pre-hospital-care providers (EMTs or paramedics) often use the fingernail beds as a cursory indicator of distal tissue perfusion of individuals that may be dehydrated or in shock.[16] However, this test is not considered reliable in adults.[17] This is known as the CRT or blanch test. WEJ Procedure: briefly depress the fingernail bed gently with a finger. This will briefly turn the nailbed white; the normal pink colour should be restored within a second or two. Delayed return to pink colour can be an indicator of certain shock states such as hypovolemia [18] [19] Thumbnail of the right hand with cuticle (left) and hangnail (top) Nail growth record can show the history of recent health and physiological imbalances, and has been used as a diagnostic tool since ancient times.[20] Deep transverse grooves known as Beau's lines may form across the nails (not along the nail from cuticle to tip) and are usually a natural consequence of aging, though they may result from disease. Discoloration, thinning, thickening, brittleness, splitting, grooves, Mees' lines, small white spots, receded lunula, clubbing (convex), flatness, spooning (concave) can indicate illness in other areas of the body, nutrient deficiencies, drug reaction or poisoning, or Mechanical injury can result in the nail being merely local injury. Nails can also become thickened dropped. (onychogryphosis), loosened (onycholysis), infected with fungus (onychomycosis) or degenerate (onychodystrophy); for further information see nail diseases. Health and care Bluish or purple fingernail beds may be a symptom of peripheral cyanosis, which indicates oxygen deprivation. Nails can dry out, just like skin. They can also peel, break, and be infected. Toe infections, for instance, can be caused or exacerbated by dirty socks, specific types of aggressive exercise, tight footwear, and walking unprotected in an unclean environment. Nail tools used by different people may transmit infections. Nail files, "if ... used on different people, ... may spread nail fungi, staph bacteria or viruses," warns Ted Dischman, a spokesperson for the California Board of Barbering and Cosmetology.germs In fact, over 100 bacterial skin infections in 2000 were traced to footbaths in nail salons. To avoid this, new improved contactless tools can be used, for example, gel and cream cuticle removers instead of cuticle Nail (anatomy) scissors. Many people also compulsively bite their nails. Nail disease can be very subtle and should be evaluated by a dermatologist with a focus in this particular area of medicine.[21] However, most times it is a nail technician who will note a subtle change in nail disease. Inherited accessory nail of the fifth toe occurs where the toenail of the smallest toe is separated, forming a smaller, "sixth toenail" in the outer corner of the nail. Like any other nail, it can be cut using a nail clipper. Nutrition for healthy nails Vitamin A is an essential micronutrient for vision, reproduction, cell and tissue differentiation, and immune function. Vitamin D and calcium work together in cases of maintaining homeostasis, creating muscle contraction, transmission of nerve pulses, blood clotting, and membrane structure. A lack of vitamin A, vitamin D, and calcium can cause dryness and brittleness. Sources of these micronutrients include fortified milk, cereal, and juices, salt-water fish, fish-liver oils, and Damaged thumbnail some vegetables. Vitamin B12 can only be found in animal sources such as liver and kidney, fish, chicken, and dairy products and therefore can cause intake issues in vegetarian and vegan populations. Not enough B12 vitamin can lead to excessive dryness, darkened nails, and rounded or curved nail ends. Insufficient intake of both vitamin A and B, as previously described, results in fragile nails with horizontal and vertical ridges.[22] Protein is a building material for new nails, therefore low dietary protein intake may cause white nail beds. Dietary sources of this macronutrient include eggs, milk, cheese, meat, beans and legumes. A lack of protein combined with deficiencies in folic acid and vitamin C produce ‘hangnails’. Essential fatty acids play a large role in healthy skin as well as nails. As touched upon previously, essential fatty acids can be obtained through consumption of fish, flaxseed, canola oil, seeds, leafy vegetables, and nuts. Splitting and flaking of nails may be due to a lack of linoleic acid. Iron-deficiency anemia can lead to a pale color along with a thin, brittle, ridged texture. Iron deficiency in general may cause the nails to become flat or concave, rather than convex. Iron can be found in animal sources, called heme iron, such as meat, fish, and poultry, and can also be found in fruits, vegetables, dried beans, nuts, and grain products, also known as non-heme iron. Heme iron is absorbed fairly easily in comparison to non-heme iron, however both types provide the necessary bodily functions.[23] Fashion Manicures and pedicures are health and cosmetic procedures to groom, trim, and paint the nails and manage calluses. They require various tools such as cuticle scissors, nail scissors, nail clippers, and nail files. Artificial nails can also be appended onto real nails for cosmetic purposes. A person whose occupation is to cut, shape and care for nails as well as to apply overlays such as acrylic and UV Gel is sometimes called a nail technician[24] . The place where a nail technician works may be a nail salon or nail shop or nail bar. Painting the nails with nail polish (also called nail lacquer and nail varnish) is a common practice dating back to at least 3000 B.C. 85 Nail (anatomy) Non-human anatomy The nails of primates and the hooves of running mammals evolved from the claws of reptiles.[25] In contrast to nails, claws are typically curved ventrally (downwards in animals) and compressed sideways. They serve a multitude of functions — including climbing, digging, and fighting — and have undergone numerous adaptive changes in different animal taxa. Claws are pointed at their ends and are composed of two layers: a thick, deep layer and a superficial, hardened layer which serves a protective function. The underlying bone is a virtual mould of the overlying horny structure and therefore has the same shape as the claw or nail. Compared to claws, nails are flat, less curved, and do not extend far beyond the tip of the digits. The ends of the nails usually consist only of the "superficial", hardened layer and are not pointed like claws.[25] With only a few exceptions, primates retain plesiomorphic (original, "primitive") Nails are a distinguishing feature in hands with five digits, each equipped with either a nail or a claw. For example, the primate order. all prosimians (i.e. "primitive" primates or "proto-primates") have nails on all digits except the second toe which is equipped with a so called toilet-claw (i.e. important for grooming activities). The needle-clawed bushbaby (Euoticus) have keeled nails (the thumb and the first and the second toes have claws) featuring a central ridge that ends in a needle-like tip. In tree shrews all digits have claws and, unlike most primates, the digits of their feet are positioned close together, and therefore the thumb cannot be brought into opposition (another distinguishing feature of primates).[25] A study of the fingertip morphology of four small-bodied New World monkey species indicated a correlation between increasing small-branch foraging and 1. expanded apical pads, 2. developed epidermal ridges (fingerprints), 3. broadened distal parts of distal phalanges (fingertip bone), and 4. reduced flexor and extensor tubercles. This suggests that whereas claws are useful on large-diameter branches, wide fingertips with nails and epidermal ridges were required for habitual locomotion on small-diameter branches. It also indicates keel-shaped nails of Callitrichines (a family of New World monkeys) is a derived postural adaptation rather than retained ancestral condition. [26] References [1] Onumah, Neh; Scher, Richard K (May 2009). "Nail Surgery" (http:/ / emedicine. medscape. com/ article/ 1126725-overview). eMedicine. . Retrieved March 2010. [2] "Nail matrix" (http:/ / www. biology-online. org/ dictionary/ Nail_matrix). Biology Online. 2005. . Retrieved February 2010. [3] Feneis, Heinz (2000). Pocket Atlas of Human Anatomy (4th ed.). Thieme. pp. 392–95. ISBN 3-13-511204-7. [4] "Glossary of Nail Technology Terminology" (https:/ / www. nailsuperstore. com/ tips/ view. aspx?TipId=81). 2008. . Retrieved February 2010. [5] Preuss, Marti (2000). "Understanding Your Natural Nails" (http:/ / hooked-on-nails. com/ naturalnails. html). Hooked on Nails. . Retrieved February 2010. [6] Lellipop (August 2006). "Anatomy of the nail" (http:/ / www. salongeek. com/ health-safety-unatural/ 40362-anatomy-nail. html). Salon Geek. . Retrieved February 2010. [7] "Nail Anatomy" (http:/ / www. naildoctors. com/ nail_anatomy. html). Nail Doctors. 2005. . Retrieved February 2010. [8] "Glossary fo Nail Conditions" (http:/ / www. footdoc. ca/ Website Nail Conditions (A Glossary). htm). The Achilles Foot Health Centre. . [9] http:/ / books. google. com/ books?id=p8VqAAAAMAAJ& q=hyponychium+ quick& dq=hyponychium+ quick& hl=en& ei=0oSuTMSqA4O88gao4PTcBA& sa=X& oi=book_result& ct=result& resnum=1& ved=0CCUQ6AEwAA 86 Nail (anatomy) [10] Jordan, Christopher; Mirzabeigi, Edwin (2000-04-01). Atlas of orthopaedic surgical exposures (http:/ / books. google. com/ ?id=gMSW59keA4UC& pg=PA101). Thieme. p. 101. ISBN 0865777764. . [11] Wang, Quincy C; Johnson, Brett A (May 2001). "Fingertip Injuries" (http:/ / www. aafp. org/ afp/ 20010515/ 1961. html). American Family Physician. . Retrieved March 2010. [12] Ravosa, Matthew J.; Dagosto, Marian (2007). Primate origins: adaptations and evolution (http:/ / books. google. com/ ?id=C8RAGvdzedoC& pg=PA416). Springer. pp. 389–90. ISBN 0387303359. . [13] Toenail Definition - Medicine.net (http:/ / www. medterms. com/ script/ main/ art. asp?articlekey=7740) [14] Hunter, J. A. A., Savin, J., & Dahl, M. V. (2002). Clinical dermatology. Malden, Mass: Blackwell Science. p. 173. ISBN 0632059168 [15] BMJ 2007;335(7633):1288 (22 December), doi:10.1136/bmj.39420.420370.25 (http:/ / www. bmj. com/ cgi/ content/ full/ 335/ 7633/ 1288) [16] Monterey County EMS Manual (http:/ / www. co. monterey. ca. us/ health/ EMS/ pdfs/ EMSManual. pdf). Chapter XI, Patient assessment. [17] Schriger DL, Baraff LJ (Jun 1991). "Capillary refill—is it a useful predictor of hypovolemic states?" (http:/ / linkinghub. elsevier. com/ retrieve/ pii/ S0196-0644(05)82375-3). Ann Emerg Med 20 (6): 601–5. doi:10.1016/S0196-0644(05)82375-3. PMID 2039096. . [18] MedlinePlus Encyclopedia Capillary nail refill test (http:/ / www. nlm. nih. gov/ medlineplus/ ency/ article/ 003394. htm) [19] St. Luke's Hospital (http:/ / www. stlukes-stl. com/ health_content/ health_ency/ 1/ 003394. htm). Capillary nail refill test. [20] American Academy of Dermatology - Nail Health (http:/ / www. aad. org/ public/ Publications/ pamphlets/ NailHealth. htm) [21] http:/ / www. nailsmag. com/ feature. aspx?fid=762& ft=1 [22] Zempleni, J; R.B. Rucker, D.B. McCormick, J.W. Suttie (2007). Handbook of vitamins (http:/ / linus. lmu. edu) (4th ed.). . [23] Cashman MW, Sloan SB (2010). "Nutrition and nail disease". Clinics in Dermatology 28 (4): 420–425. doi:10.1016/j.clindermatol.2010.03.037. PMID 20620759. [24] "Nails and Beauty Academy Training" (http:/ / www. nailsandbeautyacademy. co. uk). 2008. . Retrieved February 2010. [25] Ankel-Simons, Friderun (2007). Primate anatomy: an introduction (3rd ed.). pp. 342–44. ISBN 0-12-372576-3. [26] Hamrick, Mark W. (1998). "Functional and adaptive significance of primate pads and claws: Evidence from New World anthropoids" (http:/ / www3. interscience. wiley. com/ journal/ 28218/ abstract). American Journal of Physical Anthropology (Wiley-Liss) 106 (2): 113–127. doi:10.1002/(SICI)1096-8644(199806)106:2<113::AID-AJPA2>3.0.CO;2-R. PMID 9637179. . (Abstract) External links • Nail Disorders and Diseases (http://www.uspedicurespa.com/blog.aspx?tag=nail disorders) - types of nail disorders: Paronychia, Onychogryphosis, Melanonychia 87 Peel (tool) 88 Peel (tool) A peel is a shovel-like tool used by bakers to slide loaves of bread, pizzas, pastries, and other baked goods into and out of an oven.[1] It is usually made of wood, with a flat carrying surface (like a shovel's blade) for holding the baked good and a handle extending from one side of that surface. Alternatively, the carrying surface may be made of sheet metal, which is attached to a wooden handle. A peel's intended functions are to: • Transfer delicate breads, pastries, et cetera into an oven where transferring them directly by hand could deform their delicate structure. • Allow food to be placed further back in an oven than could normally be reached by the baker. • Keep the baker's hands out of the hottest part of an oven, or prevent the baker from burning their hands on the hot baked goods. A peel, in this case used for pizza and also sometimes called a pizza shovel Peel (tool) 89 Prior to use, peels are often sprinkled with flour, cornmeal, or milled wheat bran, to allow baked goods to easily slide onto and off them. There are peels of many sizes, with the length of the handle suited to the depth of the oven, and the size of the carrying surface suited to the size of the food it is meant to carry (for instance, slightly larger than the diameter of a pizza). Household peels commonly have handles around 15 cm long and carrying surfaces around 35 cm square, though handles range in length from vestigial (~6 centimeters) to extensive (~1.5 meters or more), and carrying surfaces range in size from miniature (~12 centimeters square) to considerably wide (1 meter square or more). Other tools An alternative, and related, meaning of the word "peel" is a wooden pole with a smooth cross-piece at one end, which was used in printing houses of the hand-press period (before around 1850) to raise printed sheets onto a line to dry, and to take them down again once dried. The term is also sometimes used for the blade of an oar. All three meanings derive ultimately from the Latin pala, a spade. Small utensil the size of a spatula. References [1] Simmons, Marie (2008). Things Cooks Love: Implements, Ingredients, Recipes. Ben Fink photographs. Andrews McMeel. p. 283. ISBN 0740769766. Scraper (kitchen) There are several types of kitchen implements which are termed scrapers. They can be made of metal, plastics such as polyethylene, nylon, or polypropylene, wood, rubber or silicone rubber. In practice, one type of scraper is often interchanged with another or with a spatula (thus scrapers are often called spatulas) for some of the various uses. Kitchen scrapers Scraper (kitchen) 90 Bowl scraper Bowl scrapers are, as the name suggests, used to remove material from mixing bowls. Often, a plate scraper is used for this purpose, particularly since the long handle allows it to be used to remove contents of bowls as well as jars, such as mayonnaise jars; however, Long-handled scraper can be used as a bowl for bowls, dedicated scrapers are available, lacking the handle, and scraper consisting of a flat, flexible piece of plastic or silicone rubber sized for convenient holding with the palm and fingers, with a curved edge to match the curvature of the average bowl. The degree of curvature can vary from a slight curvature along one edge of a rectangle, to a complex shape composed of changing radii to adapt better to bowls of different sizes. Sometimes a hole is provided in one corner, to allow for hanging the utensil, as well as for placement of the thumb to allow for more secure grip. Prices vary from below one American dollar, to as much as $20 American. [1] The technique for use of either form of bowl scraper is essentially intuitive. Dough scraper Dough scrapers, or pastry scrapers, are more rigid implements, often made of a metal rectangle with a wooden, plastic, or metal handle running along one long edge not only for more comfortable grip, but also to add rigidity; some bowl scrapers, however, are designed to be stiff enough to serve a dual purpose and are sold as such. Occasionally, an implement resembling a putty knife is sold for this purpose.[2] ,[3] This implement is used to manipulate raw dough, by scraping it from a Dough scraper surface on which it has been rolled, as well as to slice it. It can also be called a spatula. Grill scraper A grill scraper is a device used to clean cooking grills by scraping stuck particles of food from their surface. For flat surfaced grills, their design can vary from similar to a putty knife, to a more complex device with provision to protect the hands from the hot grill surface, targeted to professional cooks and chefs[4] , to even more complex models[5] costing $100 American. Varieties sold for cleaning wire grills are also available, with notches in the edge of the blade to match the wires of the grill. Plate scraper A plate scraper consists of a plastic, wooden, or metal handle attached to a flexible rubber head. Although the original use of the implement was to remove food from plates before washing [6] , its use has evolved to more of a utilitarian implement, the bowl scraper. Plate scraper Scraper (kitchen) 91 Pan scraper The pan scraper is, as the name suggests, an implement designed for the forcible removal of tightly stuck or burned food from the bottom of pots and pans before washing. They usually resemble a putty knife with a metal blade and a metal, wood, or plastic handle, sometimes with the handle mounted at an angle to the blade to allow for more vigorous scraping parallel to the surface; others, however, are a wedge shaped piece of hard plastic molded to fit the hand and with a slightly rounded sharp edge.[7] A spatula may be used as a pan scraper Shellfish scraper A shellfish scraper is a specialized utensil used for removing meat from cooked shellfish at the dining table. It consists of a stainless steel rod about ten inches in length, with a flattened tip at one end and a forked tip at the other. [8] Crumb scraper Although not a cooking utensil, a crumb scraper is used during a meal to remove crumbs and other unwanted small debris from the surface of table, for cleanliness. Although historically, when crumb scrapers were mostly used in [9] homes, ornate designs were used , the variety most often seen currently is sized and shaped for a waiter to carry in a breast pocket, and consists of a piece of sheet metal bent into a semi-cylindrical shape closely resembling a laboratory scoopula, which is dragged across the table so that the debris is dragged towards the edge, where it can be disposed of.[10] References [1] Bowl scrapers sorted by price (http:/ / www. amazon. com/ s?keywords=bowl+ scraper& rs=284507& rh=i:aps,k:bowl+ scraper,i:garden,n:1055398,n:284507& sort=-price), Amazon.com [2] Triangular Spatula (http:/ / www. ablekitchen. com/ ProductDetails. asp?ProductCode=WC-64510) [3] Pan Scraper (http:/ / www. amazon. com/ dp/ B000638HOC) [4] Grill scrapers (http:/ / www. princecastle. com/ products/ grill_tools_161-173_scrapers. asp) [5] Ergonomic Grill Scraper (http:/ / www. princecastle. com/ products/ grill_tools_613_scraper. asp) [6] Plate Scraper (http:/ / digital. lib. msu. edu/ projects/ cookbooks/ html/ museum/ object_074. html), "Feeding America" [7] Pot or Pan Scraper (http:/ / www. recipetips. com/ glossary-term/ t--38311/ pot-or-pan-scraper. asp), Recipetips.com [8] Shellfish Scraper (http:/ / www. instawares. com/ shellfish-scraper-l-stainless. mtg-62130. 0. 7. htm#gallery) [9] Crumb Scraper (http:/ / digital. lib. msu. edu/ projects/ cookbooks/ html/ museum/ object_024. html), "Feeding America" [10] patent for a crumb scraper (http:/ / www. freepatentsonline. com/ D473988. html?highlight=crumb,scraper& stemming=on) Skin 92 Skin Skin A diagram of human skin. Skin is a soft outer covering of an animal, in particular a vertebrate. Other animal coverings such as the arthropod exoskeleton or the seashell have different developmental origin, structure and chemical composition. The adjective cutaneous means "of the skin" (from Latin cutis, skin). In mammals, the skin is the largest organ of the integumentary system made up of multiple layers of ectodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs.[1] Skin of a different nature exists in amphibians, reptiles, and birds.[2] All A close up picture of a rhinoceros skin. mammals have some hair on their skin, even marine mammals which appear to be hairless. Because it interfaces with the environment, skin plays a key role in protecting (the body) against pathogens[3] and excessive water loss.[4] Its other functions are insulation, temperature regulation, sensation, and the protection of vitamin D folates. Severely damaged skin will try to heal by forming scar tissue. This is often discoloured and depigmented. Hair with sufficient density is called fur. The fur mainly serves to augment the insulation the skin provides, but can also serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is very hard and thick, and can be processed to create leather. Reptiles and fish have hard protective scales on their skin for protection, and birds have hard feathers, all made of tough β-keratins. Amphibian skin is not a strong barrier to passage of chemicals and is often subject to osmosis. For example, a frog sitting in an anesthetic solution could quickly go to sleep. Functions Skin performs the following functions: 1. Protection: an anatomical barrier from pathogens and damage between the internal and external environment in [3] [4] bodily defense; Langerhans cells in the skin are part of the adaptive immune system. 2. Sensation: contains a variety of nerve endings that jump to heat and cold, touch, pressure, vibration, and tissue injury; see somatosensory system and haptic perception. 3. Heat regulation: increase perfusion and heatloss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat. Erector pili muscles are significant in animals. 4. Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss.[4] 5. Storage and synthesis: acts as a storage center for lipids and water 6. Absorption: oxygen, nitrogen and carbon dioxide can diffuse into the epidermis in small amounts; some animals use their skin as their sole respiration organ (in humans, the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is Skin 93 negligible")[5] 7. Water resistance: The skin acts as a water resistant barrier so essential nutrients aren't washed out of the body. Mammalian skin layers Mammalian skin is composed of two primary layers: • the epidermis, which provides waterproofing and serves as a barrier to infection; and • the dermis, which serves as a location for the appendages of skin; Epidermis Epidermis, "epi" coming from the Greek meaning "over" or "upon", is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina. The epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The main type of cells which make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, basale. Cells are formed through mitosis at the basale layer. The daughter cells (see cell division) move up the strata changing shape and composition as they die due to isolation from their blood source. The cytoplasm is released and the protein keratin is inserted. They eventually reach the corneum and slough off (desquamation). This process is called keratinization and takes place within about 27 days. This keratinized layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection. The epidermis helps the skin to regulate body temperature. Layers The epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata, changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer, called the stratum corneum, consisting of approximately 15-350 layers of dead cells strengthened and made water-resistant by the keratin. This process is called keratinization. The dead cells are then sloughed off, or desquamated, which takes place within weeks. Sublayers Epidermis is divided into the following 5 sublayers or strata:[6] • • • • • Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum germinativum (also called the"stratum basale") [also see: image rotating (1.1 mb) ] Optical coherence tomogram of fingertip, depicting stratum corneum (~500 µm thick) with stratum disjunctum on top and stratum lucidum (connection to stratum spinosum) in the middle. At the bottom superficial parts of the dermis. Sweatducts are clearly visible. Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in ears, the nose and fingertips. Skin 94 Dermis The distribution of the bloodvessels in the skin of the sole of the foot. (Corium - TA alternate term for dermis - is labeled at upper right.) A diagrammatic sectional view of the skin (click on image to magnify). (Dermis labeled at center right.) Gray's subject #234 1065 MeSH Dermis Dorlands/Elsevier Skin [7] [8] [9] Dermis The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors (nerve endings) that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as from the Stratum basale of the epidermis. The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular region. Papillary region The papillary region is composed of loose areolar connective tissue. This is named for its fingerlike projections called papillae, that extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin. Reticular region The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous, elastic, and reticular fibres that weave throughout it. These protein fibres give the dermis its properties of strength, extensibility, and elasticity. Also located within the reticular region are the roots of the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels. Skin 95 Hypodermis The hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (the hypodermis contains 50% of body fat). Fat serves as padding and insulation for the body. Another name for the hypodermis is the subcutaneous tissue. Microorganisms like Staphylococcus epidermidis colonize the skin surface. The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings. In fish and amphibians The epidermis of fish and of most amphibians consists entirely of live cells, with only minimal quantities of keratin in the cells of the superficial layer. It is generally permeable, and, in the case of many amphibians, may actually be a major respiratory organ. The dermis of bony fish typically contains relatively little of the connective tissue found in tetrapods. Instead, in most species, it is largely replaced by solid, protective bony scales. Apart from some particularly large dermal bones that form parts of the skull, these scales are lost in tetrapods, although many reptiles do have scales of a different kind, as do pangolins. Cartilaginous fish have numerous tooth-like denticles embedded in their skin, in place of true scales. Sweat glands and sebaceous glands are both unique to mammals, but other types of skin gland are found in other vertebrates. Fish typically have a numerous individual mucus-secreting skin cells that aid in insulation and protection, but may also have poison glands, photophores, or cells that produce a more watery, serous fluid. In amphibians, the mucus cells are gathered together to form sac-like glands. Most living amphibians also possess granular glands in the skin, that secrete irritating or toxic compounds.[10] Although melanin is found in the skin of many species, in reptiles, amphibians, and fish, the epidermis is often relatively colourless. Instead, the colour of the skin is largely due to chromatophores in the dermis, which, in addition to melanin, may contain guanine or carotenoid pigments. Many species, such as chameleons and flounders may be able to change the colour of their skin by adjusting the relative size of their chromatophores.[10] In birds and reptiles The epidermis of birds and reptiles is closer to that of mammals, with a layer of dead keratin-filled cells at the surface, to help reduce water loss. A similar pattern is also seen in some of the more terrestrial amphibians, such as toads. However, in all of these animals there is no clear differentiation of the epidermis into distinct layers, as occurs in humans, with the change in cell type being relatively gradual. The mammalian epidermis always possesses at least a stratum germinativum and stratum corneum, but the other intermediate layers found in humans are not always distinguishable. Hair is a distinctive feature of mammalian skin, while feathers are (at least among living species) similarly unique to birds.[10] Birds and reptiles have relatively few skin glands, although there may be a few structures for specific purposes, such as pheromone-secreting cells in some reptiles, or the uropygial gland of most birds.[10] Skin 96 Mechanics Skin has a soft tissue mechanical behavior when stretched. The intact skin is prestreched (i.e. has residual stress) like neoprene wetsuits around the diver's body. When deep cuts are made on the skin, it retracts, widening the slice hole. Human uses and culture The term "skin" may also refer to the covering of a small animal, such as a sheep, goat (goatskin), pig, snake (snakeskin) etc. or the young of a large animal. The term hides or rawhide refers to the covering of a large adult animal such as a cow, buffalo, horse etc. Skins and hides from different animals are used for clothing, bags and other consumer products, usually in the form of leather, but also furs. Skin from sheep, goat and cattle was used to make parchment for manuscripts. Skin can also be cooked to make pork rind or crackling. Detailed cross section Skin layers, of both hairy and hairless skin Skin 97 References [1] "Skin care" (analysis), Health-Cares.net, 2007, webpage: HCcare (http:/ / skin-care. health-cares. net/ oily-skin-care. php). [2] Alibardi L. (2003). Adaptation to the land: The skin of reptiles in comparison to that of amphibians and endotherm amniotes. J Exp Zoolog B Mol Dev Evol. 298(1):12-41. PMID 12949767 [3] Proksch E, Brandner JM, Jensen JM. (2008).The skin: an indispensable barrier. Exp Dermatol. 17(12):1063-72. PMID 19043850 [4] Madison KC. (2003). Barrier function of the skin: "la raison d'être" of the epidermis (http:/ / www. nature. com/ jid/ journal/ v121/ n2/ pdf/ 5601872a. pdf). J Invest Dermatol. 121(2):231-41. doi:10.1046/j.1523-1747.2003.12359.x PMID 12880413 [5] Stücker, M., A. Struk, P. Altmeyer, M. Herde, H. Baumgärtl & D.W. Lübbers (2002). The cutaneous uptake of atmospheric oxygen contributes significantly to the oxygen supply of human dermis and epidermis. (http:/ / jp. physoc. org/ content/ 538/ 3/ 985. full. pdf)PDF Journal of Physiology 538(3): 985–994. doi:10.1113/jphysiol.2001.013067 [6] The Ageing Skin - Structure (http:/ / pharmaxchange. info/ press/ 2011/ 03/ the-ageing-skin-part-1-structure-of-skin-and-introduction/ ) [7] http:/ / education. yahoo. com/ reference/ gray/ subjects/ subject?id=234#p1065 [8] http:/ / www. nlm. nih. gov/ cgi/ mesh/ 2011/ MB_cgi?mode=& term=Dermis [9] http:/ / www. mercksource. com/ pp/ us/ cns/ cns_hl_dorlands_split. jsp?pg=/ ppdocs/ us/ common/ dorlands/ dorland/ seven/ 000097765. htm [10] Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 129–145. ISBN 0-03-910284-X. Spatula The term spatula is used to refer to various small implements with a broad, flat, flexible blade used to mix, spread and lift materials including foods, drugs, plaster and paints. The term derives from the Latin word for a flat piece of wood or splint (a diminutive form of the Latin spatha, meaning broadsword), hence its use also for the small, flat device, often made of wood, used to depress the tongue during medical examinations of the mouth and throat. The words spade (digging tool) and spathe are similarly derived. The word spatula is known to have been used in English since 1525.[1] Design Spatulas have a handle long enough to keep the holder's hand away from what is being lifted, or flipped. The blade often has one side longer than the other. The right side (as used) tends to be longer than the left, as this is more effective for right-handed people. Left-handed spatulas exist, but are rare. The blade may be perforated with holes or slots allowing liquids to flow through. Kitchen spatula The kitchen spatula, also called a rubber scraper is a utensil with a long handle and a broad flat edge, used for mixing and scraping bowls.[2] [3] [4] Kitchen spatulas are usually made of plastic, with a wooden or plastic handle to insulate them from heat. In American English, the word spatula is often used to refer to a scraper. In popular culture The "Weird Al" Yankovic comedy film UHF features an ad for a fictional outlet store called Spatula City that sells nothing but A common kitchen spatula design spatulas. The ad features people getting very excited over receiving spatulas, including children at Christmas and wives getting them as romantic gifts. Spatula 98 Related utensils • • • • Peel Putty knife Scraper Scoopula References [1] "Etymology OnLine" (http:/ / www. etymonline. com/ index. php?search=spatula& searchmode=none). . Retrieved 2007-05-24. [2] "AskOxford.com". [3] "Merriam-Webster Online Dictionary" (http:/ / www. m-w. com/ cgi-bin/ dictionary?va=spatula). . Retrieved 2007-06-20. [4] "AskOxford.com" (http:/ / www. askoxford. com/ concise_oed/ spatula?view=uk). . Retrieved 2010-03-14. Tongs Tongs are gripping and lifting tools, of which there are many forms adapted to their specific use. Some are merely large pincers or nippers, but the greatest number fall into three classes: 1. Tongs which have long arms terminating in small flat circular ends of tongs and are pivoted close to the handle, as in the common fire-tongs, used for picking up pieces of coal and placing them on a fire. 2. Tongs consisting of a single band of metal bent round one or two bands joined at the head by a spring, as in sugar-tongs (a pair of usually silver tongs with claw-shaped or spoon-shaped ends for serving lump sugar), asparagus-tongs and the like. Silicone-tipped locking tongs designed to withstand temperatures up to 500 degrees fahrenheit 3. Tongs in which the pivot or joint is placed close to the gripping ends, such as a driller's round tongs, blacksmith's tongs or crucible-tongs. The tongs are the most-used cooking utensil when grilling, as they provide a way to move, rotate and turn the food with delicate precision. Long handled locking tongs designed for outdoor grilling Wedge (mechanical device) Wedge (mechanical device) A wedge is a triangular shaped tool, a compound and portable inclined plane, and one of the six classical simple machines. It can be used to separate two objects or portions of an object, lift an object, or hold an object in place. It functions by converting a force applied to its blunt A wood splitting wedge end into forces perpendicular (normal) to its inclined surfaces.[1] The mechanical advantage of a wedge is given by the ratio of the length of its slope to its width.[2] [3] Although a short wedge with a wide angle may do a job faster, it requires more force than a long wedge with a narrow angle. History The origin of the wedge is unknown likely because it has been in use for over 9000 years. In ancient Egyptian quarries, bronze wedges were used to break away blocks of stone used in construction. Wooden wedges, that swelled after being saturated with water, were also used. Some indigenous peoples of the Americas used antler wedges for splitting and working wood to make canoes, dwellings and other objects. Examples for lifting and separating Wedges can be used to lift heavy objects, separating them from the surface upon which they rest. They can also be used to separate objects, such as blocks of cut stone. Splitting mauls and splitting wedges are used to split wood along the grain. A narrow wedge with a relatively long taper used to finely adjust the distance between objects is called a shim, and is commonly used in carpentry. The tips of forks and nails are also wedges, as they split and separate the material into which they are pushed or driven; the shafts may then hold fast due to friction. 99 Wedge (mechanical device) 100 Examples for holding fast Wedges can also be used to hold objects in place, such as engine parts (poppet valves), bicycle parts (stems and eccentric bottom brackets), and doors. A wedge-type door stop (door wedge) functions largely because of the friction generated between the bottom of the door and the wedge, and the wedge and the floor (or other surface). Mechanical advantage The mechanical advantage of a wedge can be calculated by dividing the length of the slope by the wedge's width:[2] Cross-section of a splitting wedge with its length oriented vertically. A downward force produces forces perpendicular to its inclined surfaces. The more acute, or narrow, the angle of a wedge, the greater the ratio of the length of its slope to its width, and thus [3] the more mechanical advantage it will yield. However, in an elastic material such as wood, friction may bind a narrow wedge more easily than a wide one. This is why the head of a splitting maul has a much wider angle than that of an axe. References [1] Wedges and screws (http:/ / em-ntserver. unl. edu/ Negahban/ em223/ note16/ note16. htm), , retrieved 2009-07-29. [2] Bowser, Edward Albert (1920), An elementary treatise on analytic mechanics: with numerous examples (http:/ / books. google. com/ ?id=mE4GAQAAIAAJ) (25th ed.), D. Van Nostrand Company, pp. 202–203, . [3] McGraw-Hill Concise Encyclopedia of Science & Technology, Third Ed., Sybil P. Parker, ed., McGraw-Hill, Inc., 1992, p. 2041. Zester 101 Zester A zester (also, citrus zester or lemon zester) is a kitchen utensil for obtaining zest from lemons and other citrus fruit. A kitchen zester is approximately four inches long, with a handle and a curved metal end, the top of which is perforated with a row of round holes with sharpened rims. To operate, the zester is pressed with moderate force against the fruit and drawn across its peel. The rims cut the zest from the pith underneath. The zest is cut into ribbons, one drawn through each hole.[1] Other tools are also sometimes called zesters because they too are able to separate the zest from a citrus fruit. For example, when Microplane discovered that its surform type wood rasps had become popular as food graters and zesters, it adapted the woodworking tools and marketed them as "zester / graters". An additional form of zesting or zester is called "spin zesting" adopted from the tool known as the Zip Zester. "Spin Zesting" allows perfect abstraction of the citrus in seconds without sacrificing safety of having the blade close to your fingers. 95% of the zest is abstracted leaving out the bitter pith matter.[2] A zester zests an orange References Notes [1] James A. Beard (1970-02-16). "Man's Best Friends:Stripper and Zester" (http:/ A Microplane grater / zester in use / news. google. com/ newspapers?id=2gAOAAAAIBAJ& sjid=KHwDAAAAIBAJ& pg=7282,4788177& dq=zester). Saint Petersburg Times. . [2] "A potpourri of unusual holiday gifts for your favorite chef" (http:/ / edition. cnn. com/ 2000/ FOOD/ news/ 12/ 11/ holiday. shopping/ ). CNN. 2000-12-11. . Article Sources and Contributors Article Sources and Contributors Antenna (biology) Source: http://en.wikipedia.org/w/index.php?oldid=434927458 Contributors: Adrian, Alexei Kouprianov, Andre Engels, Androstachys, Arx Fortis, AshLin, AxelBoldt, BAxelrod, BD2412, Badjoby, Blueshifter, Bmk, Bryan Derksen, Charles Gaudette, Chris Capoccia, Daddybinro, Debivort, Dj Capricorn, Dkchana, Dumarest, Dyanega, Emperorchaos, Giancarlodessi, Hipporoo, Hoof Hearted, HorsePunchKid, IronChris, Jean-François Clet, Jfurr1981, Jon Harald Søby, Junyor, Kaarel, Kmoksy, Kugamazog, Lockley, Lotje, MK8, Mark-mitchell-aldershot, N2e, Nczempin, Nono64, Pinethicket, Prashanthns, Proton donor, Quickos, RJ Reyes, Renicrew, Shyamal, Silvonen, Snigbrook, Stemonitis, Tanzania, Tide rolls, Timo Honkasalo, Travunia, UtherSRG, Vicpeters, Webridge, Wlodzimierz, ZooFari, 63 anonymous edits Arm Source: http://en.wikipedia.org/w/index.php?oldid=435289429 Contributors: -x-kiarna-x-, 334a, A j96, A. 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