What is flexor pollicus longus muscle?

The flexor pollicis longus muscle is a skeletal muscle in the superficial layer of the anterior compartment of the forearm. It consists of a single belly, which arises from the anterior surface of the radius, extending from just below the radial tuberosity to within a few centimeters of the radiocarpal joint. The muscle fibers run obliquely distally and laterally to form a long, thin tendon, which passes through an osteofibrous tunnel formed by the flexor retinaculum and the carpal bones. The tendon then passes obliquely across the palm of the hand and inserts into the base of the distal phalanx of the thumb (pollus is Latin for thumb).

The flexor pollicis longus muscle is innervated by the anterior interosseous nerve, a branch of the median nerve. The muscle works together with the flexor pollicis brevis to flex the thumb.

Action: Flexes thumb at metacarpophalangeal and interphalangeal joints; assists with wrist flexion

Innervation: Anterior interosseus nerve (median nerve)