abductor pollicis muscle

The abductor pollicis muscle is any muscle that performs abduction of the thumb (pollicis), moving it away from the midline or central axis of the hand. This category includes both the abductor pollicis brevis (short, intrinsic) and the abductor pollicis longus (long, extrinsic).

The abductor pollicis muscles are located at the thumb side of the hand and wrist. The brevis forms part of the thenar eminence in the palm, while the longus lies in the posterior forearm with its tendon crossing over the wrist to reach the base of the first metacarpal.

The abductor pollicis muscles move the thumb away from the index finger and the palm, enabling the full range of thumb positioning necessary for pinch, grip, and opposition. This range of motion is fundamental to human manual dexterity.

Median nerve injury affects the abductor pollicis brevis, while radial nerve injury affects the abductor pollicis longus, each producing characteristic functional limitations. De Quervain's tenosynovitis involves the longus tendon sheath, and carpal tunnel syndrome affects the brevis.

The short abductor (brevis) is an intrinsic hand muscle innervated by the median nerve and produces palmar abduction of the thumb at the metacarpophalangeal joint, while the long abductor (longus) is an extrinsic forearm muscle innervated by the radial nerve and abducts the first metacarpal.