Flexor Pollicis Brevis, Anterior View

Description

Anterior palmar exposure of the thenar eminence centers on the flexor pollicis brevis, with its superficial head lying superficial and slightly lateral and its deep head positioned deeper and more medial near the first metacarpal. Just radial to it sits the abductor pollicis brevis, while the tendon of flexor pollicis longus courses deep toward the base of the distal phalanx. The first metacarpal, proximal phalanx, and trapezium form the osseous floor, and the metacarpophalangeal joint of the thumb is shown in relation to the thenar muscle bellies and their distal tendinous expansions. Small sesamoid bones at the volar aspect of the thumb metacarpophalangeal joint may be suggested where the thenar tendons redirect their pull. Understanding this anterior arrangement matters when teaching thumb flexion mechanics and when localizing thenar weakness. Injury to the recurrent branch of the median nerve, classically at risk during open carpal tunnel release or laceration near the distal flexor retinaculum, denervates flexor pollicis brevis (typically its superficial head) and abductor pollicis brevis, producing loss of palmar abduction and reduced metacarpophalangeal flexion despite preserved interphalangeal flexion via flexor pollicis longus. Deep head innervation can vary (often ulnar nerve via the deep branch), a practical point when thenar function does not match a pure median neuropathy pattern. Pattern recognition starts here. Use this artwork for gross anatomy teaching blocks on the hand, for operative anatomy figures accompanying carpal tunnel release, thenar mass excision, or thumb metacarpophalangeal joint approaches, and for rehabilitation texts explaining pinch deficits and thenar atrophy. Anatomical accuracy verified by SciePro's Medical Advisory Board.