Comparative anatomy of M. extensor carpi radialis in 9 species of
Transcription
Comparative anatomy of M. extensor carpi radialis in 9 species of
ARTICLE ORIGINAL Comparative anatomy of M. extensor carpi radialis in 9 species of domestic Mammals and in Man C. GUINTARD and F. COSSU École Nationale Vétérinaire de Nantes, Unité d’Anatomie Comparée, route de Gachet, B.P. 40706, F-44307 Nantes Cedex 03 Correspondant : Dr. C. Guintard, ENVN, Tél. : 02 40 68 77 35, Fax : 02 40 68 77 62, E-mail : [email protected] SUMMARY RÉSUMÉ As a sequel to the study published by COSSU and GUINTARD [7], this research work compares the morphology of M. extensor carpi radialis in Man and in 9 species of domestic Mammals (sheep/cats/dogs/rabbits/oxen/ horses/pigs/mice and rats). Separation into 3 broad morphological types is suggested as a way to simplify the overall plan which goes from two distinct muscles to a single one in line with a loss of the movements of pronation and supination. Anatomie comparée du muscle extenseur radial du carpe (M. extensor carpi radialis) chez 9 espèces de Mammifères domestiques et chez l’Homme. Par C. GUINTARD et F. COSSU. Faisant suite à l’étude publiée par COSSU et GUINTARD [7], ce travail de recherche compare la morphologie du muscle extenseur radial du carpe chez l’Homme et 9 espèces de Mammifères domestiques (Mouton, Chat, Chien, Lapin, Bœuf, Cheval, Porc, Souris et Rat). La séparation en trois grands types morphologiques est suggérée comme étant une voie de simplification d’un plan d’organisation général qui va de deux muscles distincts à un seul muscle, en relation avec la perte des mouvements de pronation et de supination. KEY-WORDS : comparative anatomy - M. extensor carpi radialis - domestic Mammals - Man. MOTS-CLÉS : anatomie comparée - M. extenseur radial du carpe - Mammifères domestiques - Homme. Introduction Materials and methods The descriptive anatomical study of M. extensor carpi radialis, in the main species of domestic Mammals, has enabled us to differentiate between 3 broad morphological types [7]. In Man, we note the association of a M. extensor carpi radialis longus combined with a M. extensor carpi radialis brevis [12, 14] ; on the other hand, in sheep, there is a single muscle [2, 7]. At an intermediate stages, within some Carnivores and Lagomorphs, we note a more or less clear division of the fleshy part, which is prolonged by a double tendon [3, 5]. This work aims at furthering the study published in 2000, as it involves a greater number of species of domestic Mammals, so as to offer a typology based on the morphology of the muscle, its irrigation and innervation in relation to phenomena connected with adaptation. The initial study [7] involved 5 species (Man, Cat, Dog, Rabbit and Sheep). It has been completed by 5 others species : Rat, Mouse, Pig, Cattle and Horse. The dissections were carried out on previously deep frozen animals from the autopsy department of the Nantes Veterinary school. We worked on 4 thoracic limbs of rats, 4 thoracic limbs of mice, 6 thoracic limbs of pigs, 4 thoracic limbs of bovines and 4 thoracic limbs of horses. This sample completed the initial group which comprised 6 human thoracic limbs, 4 from rabbits, 6 from cats, 4 from dogs and 2 from sheep. In each dissection, we have described the attachments of M. extensor carpi radialis, its interactions, its innervation and its blood supply. Liquid latex was injected into the arterial system, hardened by 24 hours in a deep freeze. The injection was made into a. axillaris. Revue Méd. Vét., 2003, 154, 2, 115-119 116 GUINTARD (C.) AND COSSU (F.) Results M. EXTENSOR CARPI RADIALIS IN RATS AND MICE (Fig 2) M. extensor carpi radialis runs along the cranial surface of the radius. It is a prismatic muscle which ends with a double tendon. It is attached at the level of the lateral epicondyle of the humerus, runs along at the level of the elbow crease and medially, is attached on the II and III metacarpial [10, 13]. On its lateral surface lies the m. extensor d i g i t o rum communis. m. extensor carpi radialis is crossed on its cranial side by the fleshy part of the m. extensor carpi obliquus at the distal end of the radius. On its surface, it is covered by the v. cephalica antebrachii and the adjacent nerve branches. Blood is supplied by a collateral branch of the a. brachialis : a. transversa cubiti, which merges with the a. collateralis radialis by the recurrent radial artery. In the area of the elbow crease, its innervation is achieved through fine branches of the n. radia lis. In both species, removing the perimysium covering of the muscle, makes it possible to divide the fleshy part into two (in the proximal 1/3). Each part ends in a single tendon. M. EXTENSOR CARPI RADIALIS IN PIG, HORSE AND CATTLE (Fig 2) M. extensor carpi radialis is the largest of the extensor muscles in the forearm [1, 2, 4, 6, 7, 15]. It is a muscle with a fleshy part, oval in shape, which ends in a single tendon. It is originates at the level of the lateral humeral epicondyle and inserts distally on the dorsal and proximal sides of the main metacarpal (respectively the third metacarpal in horse, the third and fourth in cattle and pig). On its lateral side, it touches the m. extensor d i g i t o ru m communis. The blood supply of the fleshy part is provided by the a. tranversa cubiti, collateral of the a. brachialis. Innervation is achieved through a main nerve branch of n. radialis. The fleshy part cannot be divided and when it is removed from its covering the tendon remains single. Discussion The anatomical study of the m. extensor carpi radialis in the five other species previously studied enabled us to clarify the morphological evolution of the muscle within animal groups, particulary within the main domestic Mammals, in comparison with Man [8, 9]. As a result we noted : - the human type : The presence of the m. extensor carpi radialis longus and the m. extensor carpi radialis brevis, Innervation comes from n. radialis, The blood supply comes from a collateral branch of a. radialis. - the type seeing in Pig, Sheep, Cow and Horse A single fleshy part, which is prolonged by a single tendon, Innervation comes from n. radialis, a stylopode b, c zeugopode 1 a. brachialis, 2 a mediana, 3 a. radialis, 4 a. récurrente radiale (BARONE, 1996), 5 a collateralis radialis, 6 a. transversa cubiti (a. radiale proximale (BARONE, 1996)), 7 a. radialis (a. radiale distale (BARONE, 1996)), 8 a. brachialis superficialis, 9 Aa radiales superficiales, 10 a. antebrachialis superfi ciellis cranialis, 11 a. radialis proximalis (a. radiale proximale (BARONE, 1996). FIG. 1. — Radial arterial system of the forearm in Man (A), Horse (B), Dog and Cat (C), Pig (D) and Cattle (E). Revue Méd. Vét., 2003, 154, 2, 115-119 COMPARATIVE ANATOMY OF M. EXTENSOR CARPI RADIALIS IN 9 SPECIES OF DOMESTIC MAMMALS AND IN MAN * anastomosis between the transversal cubital artery and the radial collateral artery _ radial system TABLE I. — Nomenclature of the radial arterial system of the forearm according to the NA/NAV, the English translation and the terms used by R. BARONE(1996). Revue Méd. Vét., 2003, 154, 2, 115-119 117 118 Blood supply comes from a collateral branch of a. bra chialis. - an intermediate type as seen in Cat and Rabbit Two fleshy parts ending in a single tendon, - an intermediate type as seen in Dog, Rat and Mouse The fleshy part divides at the level of the two distal thirds and ends in two tendons Innervation comes from n. radialis, The blood supply comes from a collateral branch of a. bra chialis. So, the division of the fleshy part of the m. extensor carpi radialis seems to become simpler in those species which have lost pronation and supination. Curiously, the cat and the rabbit show a similar type of extensor carpi radialis muscle (muscle body divided, a single tendon), considering prosupination movements have completely disappeared in the latter, and remain prominent in the former. When there are no longer two muscles but a single one, one notes that there is a substantial simplification of the blood supply system (Table I, Fig 1). Thus the radial system which, in Man, is one of the two branches stemming from a. bra chialis, no longer exists in the other species except in the shape of collaterals coming from a. brachialis and a. mediana. When BARONE [3, 4] describes this arterial supply in Man and the domestic Mammals, he uses the term of proximal radial artery in lieu of the a. transversa cubiti. One should not forget that this artery which in animals is a collateral of a. brachialis is, in Man, a collateral of a. mediana. To call the artery which irrigates the carpus area in the different animal species studied, radial artery is a misnamer. In fact, in these species, this artery represents the distal part of the radial artery in Man. Apparently, the homologue of the radial artery in Man is the transversal cubital artery in the others species studied. Indeed, the transversal cubital artery irrigates the muscle in the cranial area of the forearm, near the radius. Nevertheless, in comparison to Man, the radial arterial system of the forearm regresses in association with the loss of the supination movement in the other species. This regression is illustrated in Figure 1, in which two distinct systems of irrigation can be distinguished: - in Man : a well developed radial arterial system - in the other species : a more or less significant regression of the radial artery and a subdivision of it. GUINTARD (C.) AND COSSU (F.) Conclusion The adaptation of a species to a certain way of life and more precisely to a certain type of locomotion brings about significant morphological variations. Thus, within the main species of domestic Mammals, the loss of pronation and supination seems to be associated with a regression of the associated arterial system. This study has also enabled us to complete the initial sample and shows that the suggested typology remains valid even when it is extended to other species of domestic Mammals. 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P. : Traité de Zoologie, tome XVI, fascicule III, Masson et Cie, Paris, 1971. 1 0.—GREENE A. : Anatomy of the rat, American philosophical society Philadelphia, Philadelphia, 1935. 11.—MAY N. : The anatomy of the sheep, volume I, 4th edn, University of Queensland Press, St Lucia, 1970. 1 2. —PATURET G. : Traité d’anatomie humaine, Tome II, le Membre Supérieur et Inférieur, Masson et Cie, Paris, 1951. 1 3.—POPESKO P., RAJTO VA V. and HORAK J. : A color atlas of anatomy of small laboratory animals, volume II, Wolf, Bratislava, 1990. 14.—ROUVIERE H. : Anatomie humaine, Tome III, Membres et Système Nerveux Central, 4 th ed., Masson & Cie, Paris, 1997. 1 5.— SACK W.O. : Pig anatomy and atlas, Veterinary Textbooks, New York, 1982. 1 6.— SCHALLER O. : Illustrated Veterinary Anatomical Nomenclature, Enke, Stuttgart, 1992. Revue Méd. Vét., 2003, 154, 2, 115-119 COMPARATIVE ANATOMY OF M. EXTENSOR CARPI RADIALIS IN 9 SPECIES OF DOMESTIC MAMMALS AND IN MAN a b c d 1 radius, 2 carpus, 3 m. extensor carpi radialis, 4 m. extensor digitorum communis, 5 m. extensor carpi obliquus FIG. 2. — Dorsal aspect of the forearm in a Rat (a), a Horse (b), a Cow (c) and a Pig (d). Revue Méd. Vét., 2003, 154, 2, 115-119 119