The palmar interossei are three small, spindle-shaped muscles which lie on the interosseous spaces of metacarpal bones. The first one is located on the radial portion of palm; it arises from the ulnar side of second metacarpal bone (index finger) and it is inserted into the ulnar side of the metacarpophalangeal joint of index finger and its dorsal aponeurosis.
The second and third palmar inertossei muscles are located on the ulnar portion of hand. They originate from the fourth and fifth metacarpal bone, respectively, and are inserted into the radial side of the capsule of the metacarpophalangeal joints of the ring and little finger. Meanwhile, the first (thumb) and third metacarpal bone (middle finger) bear no palmar interossei muscles.
Action/Function
They flex the proximal phalanges of the index, ring, and little finger. They also extend their middle and distal phalanges.
Innervation
They are innervated by secondary branches of the ulnar nerve, whose root fibers spring from C8 andT1 of brachial plexus.
Blood Supply
These three small muscles receives oxygen-rich blood from branches of the deep palmar arch, which is a curving arterial branch communicating the radial and ulnar artery.
Below, picture of deep muscles of hand, showing the palmar interossei and the dorsal interossei muscles of right hand.
