Muscle · Hand

Palmaris brevis

Musculus palmaris brevis

A thin quadrilateral sheet of muscle lying in the fat just under the skin on the ulnar side of the palm, over the small-finger muscles. It is the only muscle in the hand that inserts into skin rather than bone: its fibres run across from the flexor retinaculum and the edge of the palmar aponeurosis into the dermis of the palm's ulnar border. When it contracts it wrinkles that skin and deepens the hollow of the cupped hand, which improves the grip of the palm on an object and pads the tissue lying over the ulnar nerve and artery as they enter the hand.