Abductor pollicis longus

Origin: Ulna, radial styloid process

Insertion: First metacarpal

Artery: Posterior interosseous artery

Nerve: Posterior interosseous nerve (C7, C8)

Action: Abduction, extension of thumb

Antagonist: Adductor pollicis muscle

Description:
The Abductor pollicis longus (Extensor oss. metacarpi pollicis) lies immediately below the Supinator and is sometimes united with it. It arises from the lateral part of the dorsal surface of the body of the ulna below the insertion of the Anconaeus, from the interosseous membrane, and from the middle third of the dorsal surface of the body of the radius. Passing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the Extensor pollicis brevis, and is inserted into the radial side of the base of the first metacarpal bone. It occasionally gives off two slips near its insertion: one to the greater multangular bone and the other to blend with the origin of the Abductor pollicis brevis. Variations.—More or less doubling of muscle and tendon with insertion of the extra tendon into the first metacarpal, the greater multangular, or into the Abductor pollicis brevis or Opponens pollicis.