Palmar interossei (hand)
The palmar interossei (hand) muscles are contained in the adductor-interosseous compartment in the palm of the hand. There are three of these muscles, but the flexor pollicis brevis, which is a thumb muscle in the thenar compartment, is often referred to as part of this muscle group. Palmar interossei muscles rise from the shafts of the fingers. The first muscle is generally fused with the adductor pollicis. The muscles are attached to the base of the fingers and run through the palm of the hand to the extensor mechanism. The ulnar nerve relays messages from the brain to control the movement of the forearm and hand. Extension of the IP joints and flexing of the MCP joints in the hand are controlled by these muscles. These signals trigger movement of the palmar interossei (hand) muscles, and cause the palm and fingers to adduct, or draw forward.