Flexor Pollicis Brevis: Origin, Insertion, Action & Nerve Supply

The flexor pollicis brevis is a muscle in the hand. It is one of three thenar muscles. It has both a superficial part and a deep part.

Attachment of the Flexor Pollicis Brevis
Origin: 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.
The deeper head “varies in size and may be absent. 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.

Insertion: Lateral side of the base of proximal phalanx of the thumb.

Nerve supply of the Flexor Pollicis Brevis

The lateral terminal branch of the median nerve (C8 and T1).

Blood supply of the Flexor Pollicis Brevis
Superficial palmar branch of the radial artery

Function of the Flexor Pollicis Brevis
The flexor pollicis brevis muscle flexes the thumb at the metacarpophalangeal joint and medial rotation of the 1st metacarpal bone at the carpometacarpal joint.