Abductor pollicis brevis - Musculus abductor pollicis brevis
Origin: Transverse carpal ligament, the scaphoid and trapezium
Insertion: Radial base of proximal phalanx of thumb and the thumb extensors
Nerve: Median nerve
Action: Abduction of thumb
Antagonist: Adductor pollicis muscle
The Abductor pollicis brevis (Abductor pollicis) is a thin, flat muscle, placed immediately beneath the integument. It arises from the transverse carpal ligament, the tuberosity of the navicular, and the ridge of the greater multangular, frequently by two distinct slips. Running lateralward and downward, it is inserted by a thin, flat tendon into the radial side of the base of the first phalanx of the thumb and the capsule of the metacarpophalangeal articulation.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).