Opponens pollicis muscle
Musculus opponens pollicis
Opponens pollicis is a thenar muscle at the base of the thumb that turns the thumb across the palm to meet the fingers.
At a glance
- English
- Opponens pollicis muscle
- Latin (TA2)
- Musculus opponens pollicis
- System
- Muscle
- Region
- Upper limb
- Side
- Paired, left and right
About the opponens pollicis muscle
Opponens pollicis is one of the three muscles of the thenar eminence, the fleshy pad at the base of the thumb. It lies deepest of the three, under abductor pollicis brevis and beside flexor pollicis brevis, and rests directly on the first metacarpal.
It arises from the tubercle of the trapezium and from the flexor retinaculum next to it. Its fibres run downward and laterally and attach along the whole length of the radial border and front of the first metacarpal shaft. Like the opponens of the little finger, it ends on the metacarpal rather than the phalanges, so it acts mainly on the joint between that bone and the trapezium.
Opposition is the movement that sets the human hand apart: the thumb is brought forward, rotated and turned to face the fingertips. Opponens pollicis supplies the rotation and flexion of the first metacarpal at the carpometacarpal joint that make this possible, working with abductor pollicis brevis and the short flexor. Every precise pinch and grasp depends on it. The median nerve usually serves it through its recurrent branch, though the ulnar nerve often sends it fibres as well. Its blood comes from the superficial palmar branch of the radial artery.
In carpal tunnel syndrome, long compression of the median nerve leads to wasting of the thenar pad and difficulty touching the thumb to the little finger. The recurrent branch that serves the muscle lies just under the skin of the thenar region and can be cut by a small wound there, leaving the thumb unable to oppose.
Attachments, action and supply
- Origin
- Tubercle of the trapezium and the adjacent flexor retinaculum.
- Insertion
- Whole length of the radial border and palmar surface of the first metacarpal.
- Action
- Flexes and medially rotates the first metacarpal at the carpometacarpal joint, opposing the thumb to the fingers.
- Nerve supply
- Median nerve, recurrent branch (C8, T1), often with fibres from the ulnar nerve.
- Blood supply
- Superficial palmar branch of the radial artery.
Anthromica
See the opponens pollicis muscle where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
