What muscles are innervated by the radial nerve?

The radial nerve is responsible for innervating the muscles in the posterior compartment of the arm and forearm. Specifically, it innervates the triceps brachii, which is the primary extensor of the elbow joint, and the anconeus, a small muscle that assists in elbow extension. This is why the choice that includes the triceps brachii and anconeus is the correct one.

The other options involve muscles that are not primarily innervated by the radial nerve. The biceps brachii, for example, is innervated by the musculocutaneous nerve and primarily functions as a flexor of the elbow and supinator of the forearm. The forearm flexors, which include muscles such as the flexor carpi radialis and the flexor carpi ulnaris, are primarily innervated by the median nerve and the ulnar nerve, respectively. The flexor carpi ulnaris and the hypothenar muscles are also innervated by the ulnar nerve, focusing on movements of the wrist and fingers rather than being influenced by the radial nerve.

Thus, the correct answer emphasizes the specific muscles that the radial nerve innervates, aiding in key movements of