Which nerve innervates the triceps brachii?

Which nerve innervates the triceps brachii?

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

Answer: (D)

The triceps brachii is a posterior-arm muscle whose job is to extend the elbow, so its motor supply comes from the radial nerve. The radial nerve travels through the posterior region of the arm and sends branches to all three heads of the triceps (as well as the nearby anconeus). It originates from the posterior cord of the brachial plexus with fibers from the lower roots, typically C7–C8. In contrast, the musculocutaneous nerve supplies the anterior arm muscles, the median nerve mostly forearm flexors and some hand muscles, and the ulnar nerve mainly intrinsic hand muscles (with some forearm involvement). Therefore, the nerve that innervates the triceps brachii is the radial nerve.

The triceps brachii is a posterior-arm muscle whose job is to extend the elbow, so its motor supply comes from the radial nerve. The radial nerve travels through the posterior region of the arm and sends branches to all three heads of the triceps (as well as the nearby anconeus). It originates from the posterior cord of the brachial plexus with fibers from the lower roots, typically C7–C8. In contrast, the musculocutaneous nerve supplies the anterior arm muscles, the median nerve mostly forearm flexors and some hand muscles, and the ulnar nerve mainly intrinsic hand muscles (with some forearm involvement). Therefore, the nerve that innervates the triceps brachii is the radial nerve.