Opponens pollicis muscle

The opponens pollicis muscle is an intrinsic thenar muscle of the hand.

Origin

The muscle originates primarily from the flexor retinaculum (transverse carpal ligament) and the tubercle of the trapezium bone. Its muscle belly lies deep to the other two thenar muscles, specifically the abductor pollicis brevis and flexor pollicis brevis.

Insertion

The muscle fibers of the opponens pollicis muscle run obliquely and laterally to insert along the entire length of the lateral aspect of the first metacarpal bone.

Innervation

Like the other thenar muscles, the opponens pollicis is innervated by the recurrent branch of the median nerve.

Action

Functionally, the opponens pollicis is the principal muscle for thumb opposition. It achieves this by flexing, abducting, and medially rotating the first metacarpal at the carpometacarpal joint, allowing the thumb to touch the tips of the other fingers. This action is essential for precision grip and various manipulation tasks, significantly contributing to overall hand dexterity.