Which nerve innervates the biceps brachii?

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

Answer: (C)

The main idea is which nerve supplies the motor function of the biceps brachii, the muscle that acts to flex the elbow and supinate the forearm. The biceps brachii is innervated by the musculocutaneous nerve, which arises from the lateral cords of the brachial plexus (C5–C7). This nerve travels through the coracobrachialis and then between the biceps brachii and brachialis to provide motor fibers to the biceps, enabling elbow flexion and forearm supination when the elbow is bent. It continues as the lateral antebrachial cutaneous nerve to supply sensation to the forearm.

The radial nerve, in contrast, mainly supplies the posterior arm and forearm muscles (like the triceps and many extensors) and does not innervate the biceps. The median nerve mainly innervates most of the forearm flexors (and some hand muscles), while the ulnar nerve supplies intrinsic hand muscles and some forearm muscles, not the biceps. Hence, the musculocutaneous nerve is the correct innervation for the biceps brachii.