Insertion: Thumb, proximal phalanx
Artery: Posterior interosseous artery
Nerve: Posterior interosseous nerve (C7, C8)
Action: Extension of thumb at metacarpophalangeal joint
Antagonist: Flexor pollicis longus muscle, Flexor pollicis brevis muscle
The Extensor pollicis brevis (Extensor primi internodii pollicis) lies on the medial side of, and is closely connected with, the Abductor pollicis longus. It arises from the dorsal surface of the body of the radius below that muscle, and from the interosseous membrane. Its direction is similar to that of the Abductor pollicis longus, its tendon passing the same groove on the lateral side of the lower end of the radius, to be inserted into the base of the first phalanx of the thumb.
Variations.—Absence; fusion of tendon with that of the Extensor pollicis longus.