Ace the 2026 Gross Anatomy Challenge – Master Block 2 and Flex Your Muscle Knowledge!

The triceps brachii is in the posterior arm and acts as the main elbow extensor, so its motor supply comes from the radial nerve, which serves the posterior compartment of the arm and forearm. The radial nerve originates from the posterior cord of the brachial plexus (roots C5–T1) and travels in the radial groove with the profunda brachii artery to reach and innervate the triceps (all three heads) plus the anconeus. The other nerves listed—median (mostly anterior forearm and some hand), ulnar (medial forearm and most intrinsic hand muscles), and musculocutaneous (anterior arm muscles like biceps, brachialis, coracobrachialis)—do not innervate the triceps, so they’re not correct.