Corpus: Dorsal interosseous muscles
from latin: dorsum - back; os - bone
Synonym: Dorsal interossei muscles
1. Definition
The dorsal interosseous muscles are four short, bipennate, double-headed muscles that belong to the palmar musculature of the hand and fill the spaces between the metacarpal bones (Ossa metacarpalia).
2. Anatomy
2.1. Origin
The dorsal interosseous muscles originate with their two heads on the opposing surfaces of two adjacent metacarpal bones. Thus, the first interosseous muscle originates on the ulnar side of the first metacarpal bone and on the radial side of the second metacarpal bone. The other three muscles follow this pattern.
2.2. Insertion
The short tendons of the muscles attach according to the following scheme to the proximal phalanx and the dorsal aponeuroses of the 2nd to 4th fingers:
- Dorsal interosseous muscle I: Digit II (radial side)
- Dorsal interosseous muscle II: Digit III (radial side)
- Dorsal interosseous muscle III: Digit III (ulnar side)
- Dorsal interosseous muscle IV: Digit IV (ulnar side)
3. Innervation
The innervation of the dorsal interosseous muscles is provided by the deep branch of the ulnar nerve from the brachial plexus (segments: C8 and Th1).
4. Function
The dorsal interosseous muscles cause abduction (spreading) of the fingers at the metacarpophalangeal joints and assist in the flexion of the fingers at these joints.