O: Top of ulna I: Base of the distal phalanx of digits 2 - 5 A: Flexes distal phalanges at distal interphalangeal joints of medial four digits; assists with flexion of hand
O: Humerus ulna head I: Bodies of middle phalanges of digits 2 - 5 A: Flexes middle phalanges at proximal interphalangeal joints of medial four digits; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints and hand
O: Flexor retinaculum, scaphoid and trapezium I: Lateral side of 1st metacarpal A: Draws 1st metacarpal laterally to oppose thumb toward center of palm and rotates it medially
