Flexor Pollicis Brevis Muscle, Anterior View

Description

Framed from the palmar (anterior) aspect, the illustration isolates the flexor pollicis brevis within the thenar eminence on the radial side of the hand, superficial to the first metacarpal and adjacent to the thumb metacarpophalangeal joint. Its muscle belly sits lateral to the third metacarpal axis and courses distally toward the proximal phalanx of the thumb, where its tendon blends with the volar plate and typically inserts on the lateral base of the proximal phalanx, often incorporating the radial sesamoid. Surrounding osseous landmarks include the distal radius and ulna proximally, the carpal bones forming the wrist, and the metacarpals and phalanges aligned distally. Relationships at a glance. Thumb flexion at the metacarpophalangeal joint is easy to teach in words and harder to localize in tissue, and this anterior view makes the point: flexor pollicis brevis is an intrinsic thenar muscle, distinct from the extrinsic flexor pollicis longus tendon that passes across the carpal tunnel to the distal phalanx. That distinction matters when you are sorting out thenar weakness patterns, since recurrent motor branch median neuropathy preferentially affects thenar muscles while sparing flexor pollicis longus, and in ulnar neuropathy the deep head of flexor pollicis brevis may be involved while the superficial head remains intact. Clinicians also use these landmarks when planning incisions near the thenar crease to avoid iatrogenic injury to the recurrent motor branch. Suitable for gross anatomy and upper-limb modules, hand surgery teaching files, and textbook figures contrasting intrinsic thenar muscles with extrinsic flexor tendons at the thumb. It also fits EMG and physical exam references that map specific thumb motions to individual muscles. Anatomical accuracy verified by SciePro's Medical Advisory Board.