The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles. It lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis.

Structure

The opponens pollicis muscle is one of the three thenar muscles. It originates from the flexor retinaculum of the hand and the tubercle of the trapezium. It passes downward and laterally, and is inserted into the whole length of the metacarpal bone of the thumb on its radial side.

Innervation

Like the other thenar muscles, the opponens pollicis is innervated by the recurrent branch of the median nerve. In 20% of the population, opponens pollicis is innervated by the ulnar nerve.

Blood supply

The opponens pollicis receives its blood supply from the superficial palmar arch.

Function

''Opposition of the thumb'' is a combination of actions that allows the tip of the thumb to touch the tips of other fingers. The part of apposition that this muscle is responsible for is the flexion of the thumb's metacarpal at the first carpometacarpal joint. This specific action cups the palm. Many texts, for simplicity, use the term ''opposition'' to represent this component of true apposition. In order to truly appose the thumb, the actions of a number of other muscles are needed at the thumb's metacarpophalangeal joint. Note that the two opponens muscles (opponens pollicis and opponens digiti minimi) are named so because they oppose each other, but their actions appose the bones.

Additional images

Image:Gray426.png, The muscles of the thumb Image:Musculusopponenspollicis.png, The muscles of the right hand. Palmar surface. File:Dissection of hand.jpg, Opponens pollicis muscle Image:Gray219.png, Bones of the left hand. Volar surface. Image:Carpal-Tunnel.svg, Transverse section across the wrist and digits. File:Slide1MAI.JPG, Muscles of hand. Cross section.

References

{{Authority control Muscles of the upper limb