Radial nerve

[2] The radial nerve originates as a terminal branch of the posterior cord of the brachial plexus.

The radial nerve originates from the posterior cord of the brachial plexus with root values of C5 to C8 and T1.

In the arm, it runs behind the brachial artery and then enters the lower triangular space to reach the radial sulcus on the back of the humerus.

After it emerges out from the radial sulcus, it supplies the brachialis, brachioradialis and extensor carpi radialis longus.

[4] It is commonly believed that the radial nerve provides motor innervation to the long head of the triceps.

Radial nerve of the right axilla, posterior view
Cutaneous innervation of the right upper extremity. Areas innervated by the radial nerve are colored in pink.
Muscles of the posterior forearm. All the labelled muscles (that is, all the visible muscles except the ones on the dorsal hand and one at top left) are innervated by the radial nerve, and represent all muscles innervated by the radial nerve except for the supinator .
Radial nerve