Flexor Pollicis Brevis

The Flexor Pollicis Brevis has a large superficial portion arising from the flexor retinaculum and a smaller deep portion arising from the trapezium, trapezoid, and the first metacarpal. The flexor pollicis brevis inserts into the proximal phalanx (radial sesamoid) of the thumb. The motor recurrent branch of the median nerve innervates the flexor pollicis brevis, abductor pollicis brevis, and opponens pollicis muscles.