The palmar interossei are intrinsic muscles of the hand. There are three palmar interossei muscles (although some texts describe a fourth muscle at the base of the proximal phalanx of the thumb).
- Attachments: Each interossei originates from a medial or lateral surface of a metacarpal, and attaches into the extensor hood and proximal phalanx of same finger.
- Actions: Adduction of the digits. Assists in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints.
- Innervation: Ulnar nerve.
- Blood Supply: Palmar metacarpal arteries