The opponens pollicis performs one of the most important functions of the human hand: the ability to bring the thumb away from the fingers so that we can grasp objects. The abductor pollicis brevis pulls the thumb away from the index finger, and the flexor pollicis brevis bends the thumb toward the small finger. It is comprised of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. The thenar muscle group is found at the base of the thumb, forming the muscle bulk on the thumb side of the hand. The opponens allows us to cup our hands, bringing the small finger towards the thumb. The flexor allows the small finger to bend at the MCP joint. The abductor allows the small finger to pull away from the ring finger. They form the muscle bulk on the small finger side of the hand. The hypothenar muscle group is formed by three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. This action provides strength and stability when pinching. In addition to pulling the index finger away from the middle finger, it also pulls the thumb towards the index finger. It forms the contour between the thumb and index finger when looking at the top of the hand and is often the first muscle to shrink in patients with severe cubital tunnel syndrome due to damage of the ulnar nerve. The first dorsal interosseous muscle is the largest and originates from the 1st and 2nd hand bones. The palmar interossei pull our fingers together. While all interossei bend the MCP joints, the dorsal interossei allow us to spread our fingers away from each other. There are four dorsal and three palmar interossei muscles. The interossei muscles begin between the bones of the hand. Hand Muscles Interossei (dorsal and palmar) Other muscles, like the skeletal muscle that moves the arm, is controlled by the somatic or voluntary nervous system. There are different types of muscle, and some are controlled automatically by the autonomic nervous system. Muscles are groups of cells in the body that have the ability to contract and relax.

Abduction definition anatomy