Gross Anatomy Block 2 Practice Test 2026 – Comprehensive Exam Prep

The posterior forearm houses the extensor muscles, and their motor supply comes from the radial nerve. In the forearm, the deep branch of the radial nerve becomes the posterior interosseous nerve, which powers most of the extensor compartment. The radial nerve before this branching also gives innervation to brachioradialis and extensor carpi radialis longus. The other nerves listed mainly serve muscles in the anterior forearm or the arm and do not innervate the posterior extensors. Therefore, the nerve responsible for the posterior forearm is the radial nerve.