Insertion: Proximal phalanges
Artery: Dorsal metacarpal artery and palmar metacarpal artery
Nerve: Deep branch of ulnar nerve
Action: Abduct finger
Antagonist: Palmar interossei muscles
The Interossei dorsales (Dorsal interossei) are four in number, and occupy the intervals between the metacarpal bones. They are bipenniform muscles, each arising by two heads from the adjacent sides of the metacarpal bones, but more extensively from the metacarpal bone of the finger into which the muscle is inserted. They are inserted into the bases of the first phalanges and into the aponeuroses of the tendons of the Extensor digitorum communis. Between the double origin of each of these muscles is a narrow triangular interval; through the first of these the radial artery passes; through each of the other three a perforating branch from the deep volar arch is transmitted.
The first or Abductor indicis is larger than the others. It is flat, triangular in form, andarises by two heads, separated by a fibrous arch for the passage of the radial artery from the dorsum to the palm of the hand. The lateral head arises from the proximal half of the ulnar border of the first metacarpal bone; the medial head, from almost the entire length of the radial border of the second metacarpal bone; the tendon is inserted into the radial side of the index finger.
The second and third are inserted into the middle finger, the former into its radial, the latter into its ulnar side.
The fourth is inserted into the ulnar side of the ring finger.