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Muscle in the thenar compartment From Wikipedia, the free encyclopedia
The flexor pollicis brevis is a muscle in the hand that flexes the thumb. It is one of three thenar muscles.[1][2] It has both a superficial part and a deep part.
| Flexor pollicis brevis muscle | |
|---|---|
Superficial muscles of the left hand, palmar view. | |
| Details | |
| Origin | Trapezium, flexor retinaculum |
| Insertion | Thumb, proximal phalanx |
| Artery | Superficial palmar arch |
| Nerve | Recurrent branch of the median nerve, deep branch of ulnar nerve (medial head) |
| Actions | Flexes the thumb at the first metacarpophalangeal joint |
| Antagonist | Extensor pollicis longus and brevis |
| Identifiers | |
| Latin | musculus flexor pollicis brevis |
| TA98 | A04.6.02.055 |
| TA2 | 2522 |
| FMA | 37378 |
| Anatomical terms of muscle | |
The muscle's superficial head arises from the distal edge of the flexor retinaculum and the tubercle of the trapezium, the most lateral bone in the distal row of carpal bones.[1] It passes along the radial side of the tendon of the flexor pollicis longus.
The deeper (and medial) head "varies in size and may be absent."[3] It arises from the trapezoid and capitate bones on the floor of the carpal tunnel, as well as the ligaments of the distal carpal row.[3]
Both heads become tendinous and insert together into the radial side of the base of the proximal phalanx of the thumb;[2] at the junction between the tendinous heads there is a sesamoid bone.[4]
The superficial head is usually innervated by the lateral terminal branch of the median nerve.[1] The deep part is often innervated by the deep branch of the ulnar nerve (C8, T1).[2][3]
The flexor pollicis brevis receives its blood supply from the superficial palmar branches of radial artery.[5]
The flexor pollicis brevis flexes the thumb at the metacarpophalangeal joint,[1] as well as flexion and medial rotation of the 1st metacarpal bone at the carpometacarpal joint.[3]
Flexor pollicis brevis can, rarely, be completely absent at birth due to a congenital issue (as can the other muscles of the thenar eminence).[6]
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