Dorsal interossei muscles of hand

At a glance

English

Dorsal interossei muscles of hand

Latin (TA2)

Musculi interossei dorsales manus

System

Muscle

Region

Upper limb

Side

Paired, left and right

Arises from

The first metacarpal bone, fourth metacarpal bone, second metacarpal bone and third metacarpal bone

About the dorsal interossei muscles of hand

The spaces between the metacarpal bones are filled by the interosseous muscles, arranged in a palmar and a dorsal set. The dorsal interossei lie nearer the back of the hand, one in each space between neighbouring metacarpals. They can be felt between the bones on the back of the hand, and the first of them, between thumb and index finger, forms the fleshy web that bulges when the thumb is pressed against the side of the index.

Each dorsal interosseous is bipennate, taking origin by two heads from the facing sides of the two metacarpals bordering its space, with a larger share from the bone of the finger it serves. Its tendon passes behind the deep transverse metacarpal ligament and attaches to the side of a proximal phalanx at its base and to the extensor expansion. Their pull is always directed away from the line of the middle finger, so the first attaches to the radial side of the index, the second and third to the two sides of the middle finger, and the fourth to the ulnar side of the ring finger. The thumb and little finger have no dorsal interosseous, as they have their own abductors. The radial artery passes between the two heads of the first muscle to reach the palm, and perforating arteries pass between the heads of the others.

These muscles draw the index and ring fingers away from the midline of the hand, and move the middle finger to either side. Because their tendons pass in front of the axis of the knuckle joints and join the extensor expansion, they also flex the metacarpophalangeal joints and extend the interphalangeal joints, the position used for holding a card flat between straight fingers. The first muscle also steadies the index finger for pinching and helps to bring the thumb towards it.

All take their nerve supply from the ulnar nerve's deep branch (C8, T1), and they receive blood from the dorsal and palmar metacarpal arteries. In ulnar nerve damage the muscles waste, leaving grooves between the metacarpals on the back of the hand and the fingers cannot be spread against resistance.

Attachments, action and supply

Origin

Adjacent sides of the two metacarpals bordering each space, by two heads.

Insertion

Proximal phalanx bases and extensor expansions: radial side of index, both sides of middle finger, ulnar side of ring finger.

Action

Draw the index and ring fingers away from the middle finger's axis and move the middle finger to either side; flex the metacarpophalangeal joints and extend the interphalangeal joints.

Nerve supply

Ulnar nerve, deep branch (C8, T1).

Blood supply

Dorsal and palmar metacarpal arteries, from the dorsal carpal network and the deep palmar arch.