Which term is the muscle that closes the thumb against the palm?

Which term is the muscle that closes the thumb against the palm?

• A. Opponens pollicis
• B. Psoas major
• C. Epimysium
• D. Falciform process

Answer: (A)

Opposition of the thumb is the movement that brings the pad of the thumb across the palm to touch the other fingers, effectively closing the thumb against the palm. The muscle that does this most specifically is the opponens pollicis, a thenar muscle. It originates from the flexor retinaculum and the trapezium and inserts along the lateral side of the first metacarpal. When it contracts, it rotates and pulls the thumb across the palm, enabling grasping and pincer movements. The other options aren’t involved in this motion: a hip flexor, a connective tissue sheath around a muscle, or a liver ligament don’t control thumb opposition.

Opposition of the thumb is the movement that brings the pad of the thumb across the palm to touch the other fingers, effectively closing the thumb against the palm. The muscle that does this most specifically is the opponens pollicis, a thenar muscle. It originates from the flexor retinaculum and the trapezium and inserts along the lateral side of the first metacarpal. When it contracts, it rotates and pulls the thumb across the palm, enabling grasping and pincer movements. The other options aren’t involved in this motion: a hip flexor, a connective tissue sheath around a muscle, or a liver ligament don’t control thumb opposition.