Interosseous muscles are innervated by the deep branch of which nerve?

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

Answer: (B)

Interosseous muscles in the hand are intrinsic muscles responsible for finger abduction and adduction. They receive motor supply from the deep branch of the ulnar nerve, which after the ulnar nerve passes into the hand via Guyon’s canal travels deep to the hypothenar muscles to innervate the interossei (and the adductor pollicis and deep head of the flexor pollicis brevis). The median nerve supplies the lateral two lumbricals and most thenar muscles, not the interossei; the radial nerve supplies the extensor compartments of the arm and forearm; the musculocutaneous nerve supplies the anterior arm muscles. Therefore, the deep branch of the ulnar nerve is the correct source of innervation for the interosseous muscles.