Flexor Pollicis Brevis Under the Skin, Anterior View

Description

Anterior palmar skin has been removed to expose the thenar eminence of an adult male hand, with the flexor pollicis brevis highlighted within the superficial thenar muscle mass. The flexor pollicis brevis lies lateral to the adductor pollicis and typically medial or deep to abductor pollicis brevis, with its fibers coursing distally toward the base of the proximal phalanx of the thumb and the radial sesamoid at the metacarpophalangeal joint. Just deep and proximal, the tendon of flexor pollicis longus enters the thumb, while the first metacarpal and trapezium form the bony bed of the thenar compartment. Small but decisive. Emphasizing flexor pollicis brevis in an anterior view matters because it clarifies thenar mechanics at the thumb metacarpophalangeal joint, where flexion couples with opposition and pinch. The muscle’s dual innervation pattern is a frequent teaching point, its superficial head commonly supplied by the recurrent branch of the median nerve and its deep head often supplied by the deep branch of the ulnar nerve, which helps explain mixed patterns of thenar weakness after carpal tunnel syndrome, ulnar neuropathy in Guyon’s canal, or iatrogenic injury during release procedures. This relationship is also relevant when distinguishing isolated flexor pollicis longus dysfunction (anterior interosseous syndrome) from thenar motor loss. Use this artwork for gross anatomy lab manuals, hand surgery texts describing thenar approaches to the first carpometacarpal joint, and clinical teaching on median nerve motor testing and thenar atrophy patterns in long-standing compression neuropathy. It also supports rehabilitation and occupational therapy materials that need an accurate map of the thenar muscles for pinch strength retraining and post-operative tendon transfer planning. Anatomical accuracy verified by SciePro's Medical Advisory Board.