Which nerve innervates the hypothenar muscles?

• A. Median nerve
• B. Radial nerve
• C. Musculocutaneous nerve
• D. Ulnar nerve

Answer: (D)

The essential idea is which nerve supplies the little-finger side muscles of the hand. The hypothenar group—abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi—are intrinsic hand muscles located on the ulnar (medial) side. They receive motor input from the deep branch of the ulnar nerve, which innervates most of the hand’s intrinsic muscles on that side and enables movements of the little finger. The median nerve mainly handles the thenar muscles on the thumb side and the lateral two lumbricals, not the hypothenar group; the radial nerve supplies extensor compartments and dorsal hand muscles; the musculocutaneous nerve acts in the arm, not the hand. So the ulnar nerve best fits as their innervation.