The opponens pollicis is a short muscle of the ball of thumb, on the radial side of palm. It is shaped like a thin triangular sheet, which lies under the abductor pollicis brevis muscle. It arises from the crest of the trapezium (carpal bone) and from the anterior annular ligament. Then it runs downwards and laterally to be inserted into the whole length of the radial border of the first metacarpal bone (of thumb).
Action
The opponens pollicis pulls the first metacarpal bone inwardly towards the center of palm, opposing the other four fingers.
Innervation
This small muscle is innervated by the median nerve, which emerges from C6 and C7 of brachial plexus.
Blood Supply
It is supplied by a palmar branch of radial artery, which forms the deep palmar arch.
Below, image of palm of right hand, showing the opponens pollicis muscle. The abductor pollicis brevis has been cut away to expose it.
