Which nerve is responsible for the innervation of the biceps muscle?

The musculocutaneous nerve is responsible for the innervation of the biceps muscle. This nerve arises from the lateral cord of the brachial plexus and primarily supplies the anterior compartment of the arm, which includes the biceps brachii, brachialis, and coracobrachialis muscles. The biceps muscle is essential for elbow flexion and forearm supination, and its function depends on proper innervation through the musculocutaneous nerve.

When considering the other nerves, the ulnar nerve primarily innervates the muscles of the forearm and hand, particularly those that control fine motor skills and grip strength, but it does not innervate any muscles in the upper arm, including the biceps. The axillary nerve innervates the deltoid and teres minor muscles and is primarily responsible for the abduction of the shoulder, not the biceps. The radial nerve is mainly associated with the posterior compartment of the arm and forearm, innervating extensor muscles, but it does not innervate the biceps muscle. Therefore, the musculocutaneous nerve is the correct answer, as it uniquely provides the necessary innervation for the biceps brachii.