The muscular branches of the radial nerve supply the triceps brachii, anconæus, brachioradialis, and extensor carpi radialis longus, and are grouped as medial, posterior, and lateral.

The posterior muscular branch, of large size, arises from the nerve in the groove between the triceps brachii and the humerus.

It divides into filaments, which supply the medial and lateral heads of the triceps brachii and the anconæus muscles.

The branch for the latter muscle is a long, slender filament, which descends in the substance of the medial head of the triceps brachii.

This article incorporates text in the public domain from page 943 of the 20th edition of Gray's Anatomy (1918)