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MUSCULAR SYSTEM (Anatomy 1)

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Originally appearing in Volume V19, Page 52 of the 1911 Encyclopedia Britannica.
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MUSCULAR SYSTEM (Anatomy 1). The muscular tissue (Lat. musculus, from a fancied resemblance of certain muscles to a little mouse) is of three kinds: (1) voluntary or striped muscle; (2) involuntary or unstriped muscle, found in the skin, walls of hollow viscera, coats of blood and lymphatic vessels, &c.; (3) heart muscle. The microscopical differences of these different kinds are discussed in the article on CONNECTIVE Tissuas. Here only the voluntary muscles, which are under the control of the will, are to be considered. The voluntary muscles form the red flesh of an animal, and are the structures by which one part of the body is moved at will upon another. Each muscle is said to have an origin and an insertion, the former being that attachment which is usually more fixed, the latter that which is more movable. This distinction, however, although convenient, is an arbitrary one, and an example may make this clear. If we take the pectoralis major, which is attached to the front of the chest on the one hand and to the upper part of the arm bone on the other, the effect of its contraction will obviously be to draw the arm towards the chest, so that its origin under ordinary circumstances is said to be from the chest while its insertion is into the arm; but if, in climbing a tree, the hand grasps a branch above, the muscular contraction will draw the chest towards the arm, and the latter will then become the origin. Generally, but not always, a r For physiology, see MUSCLE AND NERVE.muscle is partly fleshy and partly tendinous; the fleshy contractile part is attached at one or both ends to cords or sheets of white fibrous tissue, which in some cases pass round pullies and so change the direction of the muscle's action. The other end of these cords or tendons is usually attached to the periosteum of bones, with which it blends. In some cases, when a tendon passes round a bony pulley, a sesamoid bone is developed in it which diminishes the effects of friction. A good example of this is the patella in the tendon of the rectass femoris (fig. 1, P.). Every muscle is supplied with blood vessels and lymphatics (fig. 1, v, a, 1), and also with one or more nerves. The nerve supply is very important both from a medical and a morphological point of view. The approximate attachments are also important, because unless they are realized the action of the muscle cannot be understood, but the exact attachments are perhaps laid too great stress on in the anatomical teaching of medical students. The study of the actions of muscles is, of course, a physiological one, but teaching the subject has been handed over to the anatomists, and the results have been in some respects unfortunate. Until very recently the anatomist studied only the dead body, and his one idea of demonstrating the action of a muscle was to expose and then to pull it, and whatever happened he said was the action of that muscle. It is now generally recognized that no movement is so simple that only one muscle is concerned in it, and that what a muscle may do and what it really does do are not necessarily the same thing. As far as the deeper muscles are concerned, we still have only the anatomical method to depend upon, but with the superficial muscles it should be checked by causing a living person to perform certain movements and then studying which muscles take part in them. For a modern study of muscular actions, see C. E. Beevor's Croonian Lectures for 1903 (London, 1904). Muscles have various shapes: they may be fusiform, as in fig. 1, conical, riband-like, or flattened into triangular or quadrilateral sheets. They may also be attached to skin, cartilage or fascia instead of to bone, while certain muscles surround openings which they constrict and are called sphincters. The names of the muscles have gradually grown up, and no settled plan has been used in giving them. Sometimes, as in the coraco-brachialis and thyro-hyoid, the name describes the origin and insertion of the muscle, and, no doubt, for the student of human anatomy this is the most satisfactory plan, since by learning the name the approximate attachments are also learnt. Sometimes the name only indicates some peculiarity in the shape of the muscle and gives no clue to its position in the body or its attachments; examples of this are biceps, semitendinosus and pyriformis. Sometimes, as in the flexor carpi ulnaris and corrugator supercilii, the use of the muscle is shown. At other times the position in the body is indicated, but not the attachments, as in the tibialis anticus and peroneus longus, while, at other times, as in the case of the pectineus, the name is only misleading. Fortunately the names of the describers themselves are very seldom applied to muscles; among the few examples are Horner's muscle and the R, The fleshy belly. to, Tendon of origin. ti, Tendon of insertion. n, Nerve of supply. a, Artery of supply. v, Vein. 1, Lymphatic vessel. P, The patella. muscular band of Treitz. The German anatomists at the Easel conference lately proposed a uniform Latin and Greek nomenclature, which, though not altogether satisfactory, is gaining ground on the European continent. As there are some four hundred transverse wrinkles in the forehead. The anterior, posterior and superior auricular muscles are present but are almost functionless in man. The orbicularis palpebrarum forms a sphincter round the eyelids, which it closes, though there is little doubt that parts of the muscle can act separately and cause various expressions. The side of From A. M. Paterson, Cunningham's Text Book of Anatomy. Epicranial aponeurosis
End of Article: MUSCULAR SYSTEM (Anatomy 1)
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