Flexor pollicis brevis

The flexor pollicis brevis (Latin: musculus flexor pollicis brevis) is a short, thin and wide muscle of the hand. Together with the adductor pollicis, abductor pollicis brevis and opponens pollicis, it forms thenar eminence on the lateral (radial) side of the palm. Therefore, the flexor pollicis brevis is also known as one of the four thenar muscles (muscles of the thumb). It lies medial to the opponens pollicis, inferior to the abductor pollicis brevis and superior to the adductor pollicis. The flexor pollicis brevis is composed of two heads - superficial and deep.

Flexor pollicis brevis
Origin

Superficial head - trapezium bone, flexor retinaculum

Deep head - trapezoid and capitate bones

InsertionBase of proximal phalanx of thumb
ActionThumb flexion
Innervation

Superficial head - recurrent branch of median nerve

Deep head - deep branch of ulnar nerve

Blood supplySuperficial palmar, radialis indicis and princeps pollicis arteries

Origin

The superficial head of the flexor pollicis brevis muscle originates from the flexor retinaculum and trapezium. The deep head originates from the trapezoid and capitate bones.

Insertion

The flexor pollicis brevis inserts on the base (lateral part) of the proximal phalanx of the first finger.

Action

The flexor pollicis brevis muscle provides the flexion of the thumb at the first carpometacarpal and metacarpophalangeal joints.

Innervation

Both heads of the flexor pollicis brevis are supplied by different nerves. The superficial head is innervated by the recurrent branch of the median nerve, while the deep head is innervated by the deep branch of the ulnar nerve.

Blood supply

The flexor pollicis brevis muscle receives arterial blood supply from the superficial palmar, radialis indicis and princeps pollicis arteries. All are branches of the radial artery.