Brachialis
The most frequent varieties of the muscle consist of its subdivision into two or more parts. When the muscle is divided, the distal insertions are irregular and variable. The parts may be attached to the coronoid process of the ulna, radius on or below the tuberosity, radius and ulna, radius and a tendinous band between it and the coronoid process, fascia of the forearm (the part or slip is then named brachiofascialis of Wood), or muscles of the forearm arising from the medial epicondyle.
Another example of brachiofascialis (Wood) is provided by Reid and Taylor, "a slip from biceps, about the size of the forefinger, passed down over the brachial artery to be inserted into the deep fascia over pronator teres. The muscular slip was 2.5 inches (6.1+ cm.) in length and fusiform in shape."
A slip from brachialis may pass to the semilunar fascia and a deep detached bundle has been observed attached to the capsule of the elbow joint (capsularis subbrachialis). The brachialis muscle is sometimes closely connected or even fused with brachioradialis and extensor carpi radialis; it may also be absent. Brachialis may be innervated by three nerves: musculocutaneous , from the muscles superior surface; the median, on its medial distal edge: and the radial, on its lateral distal edge.
The anterior interosseous nerve syndrome may result from a fibrous band arising from the brachialis fascia and usually also involves the pronator teres muscle. The syndrome is a nerve entrapment neuropathy of a motor branch of the median nerve resulting in paresis or paralysis of its muscle units; the flexor pollicis longus, flexor digitorum profundus of the index and sometimes the middle finger, and pronator quadratus.
Syn.: m. brachiaeus internus, brachialis internus, brachialis anterior, flexor antibrachii ulnaris, Supinator longus, Ellenbogenbeuger, Innerer Armmuskel.
References
Calori, L. (1866) Delle corrispondenze del nervo muscolo-cutaneo con il capo soprannumerario del bicipite bracchiale e col bracchiale interno. Mem. Roy. Accad. Sci. Istituto Bologna 6:149-155.
Chuquet, -. (1876) Ossification développée au niveau du tendon brachial anterior. Bulletins et Mem. de la Société Anatomique de Paris LI(12):726-727.
Godlewski, E. (1904) Note sur la constitution des insertions inferieures du muscle brachial anterieur. L'Assoc. Anatomistes, Comptes Rendus. 6:146-148.
Gruber, W. (1848) Seltene Beobachtungen aus dem Gebiete der menschlichen Anatomie. S.4,5. Ueber zwei eigenthumliche losgetrennte und zum Radius gehende Bundel des Musculus brachialis internus. Arch. Anat. Physiol. Wissen. Med. 1848: 410-433.
Henle, J. (1871) Handbuch der Muskellehre des Menschen, in Handbuch der systematischen Anatomie des Menschen. Verlag von Friedrich Vieweg und Sohn, Braunschweig.
Hill, N.A., Howard, F.M. and B.R. Huffer. (1985) The incomplete anterior interosseous nerve syndrome. J. Hand Surg. A 10:4-16.
Ip, M.C. and K.S.F. Chang (1968) A study on the radial supply of the human brachialis muscle. Anat. Rec. 162: 363-370.
Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40:195-300.
Reid, R.W. and S.Taylor. (1879) Anatomical variations. Reports. St. Thomas's Hospital 9:46-47.
Spinner, M. (1970) Anterior interosseous nerve syndrome, with special attention to its variations. J. Bone Joint Surg. A 52:84-94.
Wolf-Heidegger, W. Contribution à l'étude des anomalies des muscles biceps brachial et brachial antérieur. Arch. d'Anat. d'Histol. et Embryol. 23:207-217.
