著者

本間 敏彦 坂井 建雄

出版者

Primate Society of Japan

雑誌

霊長類研究 (ISSN:09124047)

巻号頁・発行日

vol.8, no.1, pp.25-31, 1992 (Released:2009-09-07)

参考文献数

23

被引用文献数

2

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Anatomy of the intrinsic and extrinsic hand muscles concerning the thumb movement were studied in 6 primate species including tree shrews, slow lorises, a squirrel monkey, crab-eating monkeys, an orangutan and man. Four thenar muscles which represent the intrinsic muscles are found in all the species examined except for the tree shrews which lack M. opponens pollicis. This muscle effects an opposable movement of the thumb against the other fingers in the prosimians and the higher primates. The opposable movement which enables grasping of tools is most effective in the man. Among the four extrinsic muscles, M. extensor pollicis brevis (EPB) and M. flexor pollicis longus (FPL) are unique in the man. In the other species examined, the former is totally absent and the latter may be represented by a tendon coming from M. flexor digitorum profundus. EPB and FPL work together to flex specifically the phalangeal joint of the thumb without bending the other joints. Thereby FPL flexes the distal phalanx and the EPB stabilizes the proximal phalanx. In the other primates, flexion of the joint is inevitably accompanied by bending of the distal phalangeal joints of the other fingers, as seen in the human toes.