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The Opponens Pollicis Muscle is a small, triangular muscle that originates from the flexor retinaculum and the tubercle of the trapezium, and inserts into the radial side of the metacarpal bone of the thumb. It lies lateral to the flexor pollicis brevis muscle and deep to the abductor pollicis brevis muscle. It is innervated by the median nerve and receives its vascular supply from the superficial palmar arch [rx].
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, lying deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis.
Structure of Opponens Pollicis Muscle
The opponens pollicis 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.
Opponens pollicis muscle originates from the flexor retinaculum and tubercle of the trapezium bone. From its origin point, the muscle belly courses dorsally and laterally to insert onto the anterolateral surface of the first metacarpal shaft.
Nerve Supply of Opponens Pollicis Muscle
- 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.[rx]
- Opponens pollicis muscle is innervated by the recurrent (thenar) branch of median nerve (root value C8 and T1) and occasionally by the deep terminal branch of ulnar nerve.
Blood Supply of Opponens Pollicis Muscle
- The opponens pollicis receives its blood supply from the Superficial palmar arch.
- Princeps pollicis artery
- Radialis indicis artery
- Deep palmar arch
Function of Opponens Pollicis
Apposition 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.
As its name suggests, the main function of opponens pollicis is to produce an opposition of the thumb. The opposition refers to the rather complex movement of the thumb which is a combination of flexion, adduction and medial rotation at the first carpometacarpal joint.