Flexor pollicis longus

Flexor pollicis longus muscle
Front of the left forearm. Deep muscles. (Flexor pollicis longus is shown in blue)
Details
Origin	The middle 2/4 of the anterior surface of the radius and the adjacent interosseus membrane.
Insertion	The base of the distal phalanx of the thumb
Artery	Anterior interosseus artery
Nerve	Anterior interosseous nerve (branch of median nerve) (C8, T1)
Actions	Flexion of the thumb.
Antagonist	Extensor pollicis longus muscle, Extensor pollicis brevis muscle
Identifiers
Latin	Musculus flexor pollicis longus
TA	A04.6.02.037
FMA	38481
Anatomical terms of muscle []

The flexor pollicis longus (FPL, Latin flexor, bender; pollicis, of the thumb; longus, long) (/ˈflɛksər ˈpɒlᵻsᵻs ˈlɒŋɡəs/)) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus.

This muscle is unique to humans, being "either rudimentary or absent" in other primates.

It arises from the grooved anterior (side of palm) surface of the body of the radius, extending from immediately below the radial tuberosity and oblique line to within a short distance of the pronator quadratus muscle. An occasionally present accessory long head of the flexor pollicis longus muscle is called 'Gantzer's muscle'. It may cause compression of the anterior interosseous nerve.

It arises also from the adjacent part of the interosseous membrane of the forearm, and generally by a fleshy slip from the medial border of the coronoid process of the ulna. In 40 per cent of cases, it is also inserted from the medial epicondyle of the humerus, and in those cases a tendinous connection with the humeral head of the flexor digitorum superficialis is present.