Interossei of the Hand Under the Skin, Palmar View

Description

Presented from the palmar aspect of an adult male hand with the skin reflected, the interossei occupy the intermetacarpal spaces as bipennate muscle bellies lying deep to the superficial palmar fascia and palmar aponeurosis. Palmar interossei are positioned along the ulnar sides of the index, middle, and ring metacarpals and along the radial side of the little finger, each coursing distally toward the bases of the proximal phalanges and the extensor expansions at the metacarpophalangeal joints. Between them, the metacarpals form the bony walls of the intrinsic compartments, while the phalanges and the articular surfaces of the metacarpophalangeal and interphalangeal joints provide clear distal landmarks. Wrist-level carpal architecture and the distal radius sit proximal, establishing the longitudinal axis of the hand. Orientation is immediate. Functionally, this is the muscle group responsible for fine control of finger abduction and adduction, and for metacarpophalangeal flexion coupled with interphalangeal extension via the extensor hood. Denervation of the deep branch of the ulnar nerve (Guyon canal compression, hook of hamate fracture, or iatrogenic injury during carpal tunnel or ulnar release) produces interosseous wasting and loss of pinch coordination, with a characteristic ulnar claw pattern when the lumbricals cannot counterbalance the long extensors. For teaching intrinsic tightness and lumbrical versus interosseous action, a palmar view clarifies how these muscles sit deep to the flexor tendons yet insert into the dorsal digital expansion. Ideal applications include gross anatomy and kinesiology modules on intrinsic hand mechanics, surgical atlases for ulnar nerve pathology and palmar approaches to metacarpals, and hand therapy resources explaining interossei training after nerve repair or metacarpal fracture fixation. Anatomical accuracy verified by SciePro's Medical Advisory Board.