Anatomy

Origin

By two heads from adjacent sides of first and second, second and third, third and fourth, and fourth and fifth metacarpal bones.

Insertion

First—lateral side of base of proximal phalanx of index finger. Second—lateral side of base of proximal phalanx of middle finger. Third—medial side of base of proximal phalanx of middle finger. Fourth—medial side of base of proximal phalanx of ring finger.

Nerve

Ulnar nerve (C8, T1).

Actions

Abduct fingers away from center of third finger at metacarpophalangeal joints, assist in flexion of fingers at metacarpophalangeal joints.