Which nerve provides innervation to the adductor pollicis muscle?

• A. Ulnar, deep branch
• B. Median nerve
• C. Ulnar, superficial branch
• D. Radial nerve

Answer: (A)

Adduction of the thumb is carried out by the adductor pollicis, a deep hand muscle. Its motor supply comes from the deep branch of the ulnar nerve after the nerve enters the hand. This deep branch supplies most intrinsic hand muscles, including the interossei and the deep head of the flexor pollicis brevis, as well as the adductor pollicis. The median nerve supplies the thenar muscles (the muscles that move the thumb at the base) and the first two lumbricals, not the adductor pollicis. The superficial branch of the ulnar nerve is mainly sensory to the medial palm and digits and does not carry motor to this muscle. The radial nerve does not innervate intrinsic hand muscles. So the correct innervation is the deep branch of the ulnar nerve.