The interosseus muscles of the hand, as the name suggests, are found between ("inter") the bones ("osseus") of the hand, specifically the metacarpals. They consist of a dorsal and a palmar set of muscles.
The dorsal interossei are bipennate, the palmar interossei are unipennate
The function of these muscles is to abduct and adduct the digits. The palmar interossei ADduct, the dorsal interossei ABduct. This can be remembered with the mnemonic "PAD and DAB" - Palmar ADduct, Dorsal ABduct.
The interossei attach to the proxmial phalanx and extensor hood of each finger.
The first palmar interosseus muscle is often rudimentary due to the other muscles of the thumb involved in adduction – e.g. adductor pollicis. When present, the first palmar interosseus originates from the medial surface of the thumb arpal and inserts into the base of the proximal phalanx and the extensor hood.
Palmar interossei are smaller than dorsal.
The tendons pass deep to the deep transverse metacarpal ligaments.
The thumb and little finger have separate muscles for abduction – abductor digiti minimi and abductor pollicis brevis, therefore do not have dedicated dorsal interossei.
The radial artery passes between the heads of the first doral interosseus muscle.
The function of these muscles is to abduct and adduct the digits. The palmar interossei ADduct, the dorsal interossei ABduct. This can be remembered with the mnemonic “PAD and DAB” – Palmar ADduct, Dorsal ABduct.