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largest branch of the brachial plexus; extends down the humerus to the lateral epicondyle where it divides into one branch that goes to the skin on the back of the hand and another that goes to the underlying extensor muscles

largest branch of the brachial plexus; extends down the humerus to the lateral epicondyle where it divides into one branch that goes to the skin on the back of the hand and another that goes to the underlying extensor muscles

A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand.

Arises from the four inferior branches of the brachial plexus. It is, at first, situate behind the other nerves of the plexus. It then becomes engaged between the three portions of the triceps brachialis, passes behind the humerus, and descends between the supinator longus and brachialis internus, as far as opposite the upper extremity of the radius. In its course it gives numerous filaments to the triceps, supinator longus, extensor carpi radialis longior, and to the integuments. Opposite the upper extremity of the radius it divides into two branches; - the one posterior, which turns backwards into the substance of the supinator brevis, and when it has reached the space between the two layers of muscles on the posterior surface of the forearm, divides into a great number of filaments, which are distributed to those muscles, and to the integuments of the hand. The other branch is anterior: it descends before the supinator brevis and the radius; until, near the inferior third of that bone, it engages itself between the tendons of the supinator longus and extensor carpi radialis longior; and, becoming afterwards subcutaneous, divides into two branches, whose filaments are distributed to the integuments of the thumb, index, middle finger, to the outside of the ring finger, and to the first interosseous muscle of the back of the hand.