Revision Aid: Entry #7
Topic #7: Lumbricals and Interossei:
- There are 4 lumbricals in each hand, attached to the radial side of each finger. They originate from the tendons of flexor digitorum profundus and insert into the extensor hoods. They flex the MCP joints and extend the PIP and DIP joints. The medial 2 are supplied by the ulnar nerve, the lateral two by the median nerve.
- The palmar interossei adduct the fingers, and so originate from the appropriate sides of the 2nd 4th and 5th metacarpals. They insert on the same side into the proximal phalanx.
- The dorsal interossei abduct the fingers, and are bipennate: each sites between 2 metacarpals and is attached to both shafts. They insert into the 2nd, 3rd, 3rd and 4th extensor hoods (no typo)
- The little fingers lacks a dorsal interosseous due to its possession of abductor digiti minimi.
- All the interossei are supplied by the deep branch of the ulnar nerve.