Palmar interossei muscles

Palmar interossei muscles
Three of the palmar interossei of the left hand, inferior view
Details
Origin	Sides of metacarpals facing midline
Insertion	Bases of proximal phalanges, extensor expansions
Artery	Palmar metacarpal artery of deep palmar arch
Nerve	Deep branch of ulnar nerve
Actions	Adduction, flexion and extension of fingers
Antagonist	Dorsal interossei
Identifiers
Latin	Musculi interossei palmares
TA	A04.6.02.067
FMA	37419
Anatomical terms of muscle []

In human anatomy, the palmar or volar interossei (interossei volares in older literature) are three small, unipennate muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers. They are smaller than the dorsal interossei of the hand.

Each of the palmar interossei originate along the shaft of the metacarpal bone of the digit on which they act. They are inserted into the base of the proximal phalanx and the extensor expansion of the extensor digitorum of the same digit.

The first palmar interosseous is located at the thumb's medial side. Passing between the first dorsal interossei and the oblique head of adductor pollicis, it is inserted on the base of the thumb's proximal phalanx together with adductor pollicis.

This muscle, the so-called pollical palmar interosseous muscle (PPIM), is present in more than 80% of individuals and was first described by Henle 1858. Its presence has been verified by numerous anatomists since, but others have either fail to mention it or considered it part of either adductor pollicis or flexor pollicis brevis. However, the deep head of the flexor pollicis brevis originate on the thumb's ulnar sesamoid bone and the oblique portion of the adductor pollicis on several carpal bones as well as the bases of the second and third metacarpal bones and not on the first metacarpal.

The other three palmar interossei originate on the side of the metacarpal facing the hand's midline (ray of long finger); the second is attached to the medial side of the index finger; the third to the lateral side of the ring finger; and the fourth to the lateral side of the little finger. The tendons of these three muscles pass posterior to the deep transverse ligament before being inserted onto the extensor expansion.

All of the interosseous muscles of the hand are innervated by the deep branch of the ulnar nerve.

The palmar interossei are supplied by the palmar metacarpal artery of the deep palmar arch.