The structure indicated is the first dorsal interosseous
muscle of the hand.
The dorsal interossei
belong to the intrinsic group
of muscles which act on the hand. The intrinsic muscles include the following muscles/groups:
- Thenar group (act on thumb)
- Hypothenar group (act on little finger)
- Adductor pollicis
- Interossesus muscles (dorsal and palmar)
- Palmaris brevis
All the intrinsic muscles of the hand, except the thenar muscles and the lateral two lumbrical muscles are innervated by the deep branch of the ulnar nerve
. The thenar muscles and the lateral two lumbrical muscles are innervated by the median nerve
. A useful mnemonic for remembering this is MEATLOAF. “M
EAT” refers to the M
edian nerve, and LOAF
refers to the muscles which it innervates: L
ateral two lumbricals, O
pponens pollicis, A
bductor pollicis brevis, F
lexor pollicis brevis.
The interosseous muscles
, as the name suggests are located between (inter-) the metacarpal bones (-osseus). There are 4 bipennate dorsal interossei
located between the adjacent shafts of the metacarpal bones and insert onto the bases of the proximal phalanges and the extensor hoods. The dorsal interossei serve to abduct
the fingers away from the central axis of the middle finger. The first interosseous muscle inserts onto the base laterally on the index finger.
The palmar interossei
in contrast are unipennate
in structure and function to adduct
the fingers towards the central axis of the middle finger. A useful mnemonic for remembering this function is PAD and DAB: P
almar interossei AD
orsal interossei AB
Learn more about the anatomy of the hand muscles
in this tutorial.