Henry Gray (18251861). Anatomy of the Human Body. 1918.
and third are inserted into the middle finger, the former into its radial, the latter into its ulnar side. The fourth is inserted into the ulnar side of the ring finger.
The Interossei volares (Palmar interossei), three in number, are smaller than the Interossei dorsales, and placed upon the volar surfaces of the metacarpal bones, rather than between them. Each arises from the entire length of the metacarpal bone of one finger, and is inserted into the side of the base of the first phalanx and aponeurotic expansion of the Extensor communis tendon to the same finger.
The firstarises from the ulnar side of the second metacarpal bone, and is inserted into the same side of the first phalanx of the index finger. The secondarises from the radial side of the fourth metacarpal bone, and is inserted into the same side of the ring finger. The thirdarises from the radial side of the fifth metacarpal bone, and is inserted into the same side of the little finger. From this account it may be seen that each finger is provided with two Interossei, with the exception of the little finger, in which the Abductor takes the place of one of the pair.
As already mentioned (p. 461), the medial head of the Flexor pollicis brevis is sometimes described as the Interosseus volaris primus.
Nerves.The two lateral Lumbricales are supplied by the sixth and seventh cervical nerves, through the third and fourth digital branches of the median nerve; the two medial Lumbricales and all the Interossei are supplied by the eighth cervical nerve, through the deep palmar branch of the ulnar nerve. The third Lumbricalis frequently receives a twig from the median.
Actions.The Interossei volares adduct the fingers to an imaginary line drawn longitudinally through the center of the middle finger; and the Interossei dorsales abduct the fingers from that line. In addition to this the Interossei, in conjunction with the Lumbricales, flex the first phalanges at the metacarpophalangeal joints, and extend the second and third phalanges in consequence of their insertions into the expansions of the Extensor tendons. The Extensor digitorum communis is believed to act almost entirely on the first phalanges.
8. The Muscles and Fasciæ of the Lower Extremity. a. The Muscles and Fasciæ of the Iliac Region
The muscles of the lower extremity are subdivided into groups corresponding with the different regions of the limb.