Flexor pollicis brevis

The flexor pollicis brevis (or flexor pollicis brevis muscle, latin: musculus flexor pollicis brevis) is one of the four muscles of the thumb (also known as thenar muscles) located on the radial side of the palm.

The flexor pollicis brevis is a thin, two headed muscle lying medially from the opponens pollicis, beneath the abductor pollicis brevis and above the adductor pollicis.  The flexor pollicis brevis has two heads: the superficial and the deep head.


The superficial head of the flexor pollicis brevis originates from the flexor retinaculum, but the deep head originates from the trapezoid and trapezium bones.


The flexor pollicis brevis passes obliquely to the lateral side of the hand and inserts onto the base of the proximal phalanx of the thumb.


The flexor pollicis brevis functions as a flexor of the thumb.


The superficial head of the flexor pollicis brevis is innervated by the median nerve, while the deep head is innervated by the ulnar nerve.