Palmar interossei

The palmar interossei (Latin: musculi interossei palmares) are usually three short extrinsic muscles on the palmar side of the hand that are located in the spaces between the metacarpal bones. They extend between the metacarpal bones and proximal phalanges. Together with the dorsal interossei of the hand and lumbricals, these muscles belong to the middle group of the hand muscles. Usually, the second, fourth and fifth fingers contain the palmar interossei muscles, but the third and first fingers lack it. Opposite the dorsal interossei, the palmar interossei provide finger adduction.

Origin

The palmar interossei muscles arise from the second, fourth and fifth metacarpal bones. The first palmar interosseous muscle originates from the medial (ulnar) side of the second metacarpal bone, while the second and third palmar interossei arise from the lateral (radial) sides of the fourth and fifth metacarpal bones.

Insertion

The palmar interossei muscles insert on the bases of the second, fourth and fifth proximal phalanges of the hand and adjacent extensor expansions. The first palmar interosseous attaches to the medial (ulnar) side of the second proximal phalanx, while the second and third palmar interossei insert on the lateral (radial) sides of the fourth and fifth proximal phalanges.

Action

The primary function of the dorsal interossei muscles is to provide finger adduction at the second, fourth and fifth metacarpophalangeal joints. Like the lumbricals and dorsal interossei of the hand, these muscles also flex the proximal phalanges at the second, fourth and fifth metacarpophalangeal joints and extend the middle and distal phalanges at the second, fourth and fifth interphalangeal joints.

Innervation

The palmar interossei muscles are innervated by the deep branch of the ulnar nerve (C8 - Th1).

Blood supply

The palmar interossei muscles receive arterial blood supply from the palmar metacarpal arteries that arise from the deep palmar arch.