The abductor pollicis brevis is one of the intrinsic muscles of the hand within the thenar group.
The intrinsic muscles of the hand are involved with precision movements and consist of the following muscles:
- Thenar muscles: flexor pollicis brevis, abductor pollics brevis, opponens pollicis
- Hypothenar muscles: abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi
- Interosseus muscles
- Other: palmaris brevis, adductor pollicis
The intrinsic muscles of the hand are innervated by the deep branch of the ulnar nerve, except the tehnar muscles and the lateral two lumbricals. A mnemonic for remembering this is Meat LOAF, Meat = Median nerve innervates the Lateral lumbricals, Opponens pollicis, Abductor pollicis brevis and Flexor pollicis brevis
- Tubercles of scaphoid and trapezium and adjacent flexor retinaculum
- Radial side of the base of the proximal phalanx of the thumb, and extensor hood
The abductor pollicis brevis lies proximal to the flexor pollicis brevis
- Abduction of the thumb at the metacarpohalangeal joint of the thumb (also some action at the carpometacarpophalangeal joint)
- Assists opposition and extension of the thumb.
- Recurrent Branch of Median Nerve
The recurrent branch of the median nerve supplies the thenar muscles. But remember that the deep head of the flexor pollicis brevis is supplied by the deep branch of the ulnar nerve.
The median nere supplies sensation to the skin of the radial 3 and a half fingers (thumb, index, middle and lateral half of the ring).
The median nerve passes within the carpal tunnel and divides into the recurrent branch and palmar digital branches
- Superficial palmar arch from the radial artery