Brachial Plexus

The brachial plexus is an intricate web of nerves which originate from the cervical and thoracic roots. Located in the antero-lateral region of neck and shoulder, it is formed by the junctions of the anterior primary divisions of the lower four cervical nerves (C4, C5, C6, C7), and the upper two thoracic (T1, T2). It consists of mixed nerve fibers which innervate the upper limb. Damage to one or more nerves that make up the brachial plexus can cause partial or total paralysis of arm, forearm and hand.

Branches

The plexus is composed of three nerve cords: the lateral (outer), medial (inner), and a posterior cord, which lies in the middle of the lateral and medial. These cords give off four nerve branches that supply the muscles and skin of the arm, forearm, and hand; they are the median nerve, which supplies the flexor muscles of anterior compartment of forearm and muscles of thumb; the ulnar nerve, which supplies the flexor carpi ulnaris and the flexor digitorum profundus; the radial nerve, which innervates the triceps brachii and the extensor muscles of posterior side of forearm; and the musculocutaneous nerve, which sends branches to the coracobrachialis and biceps brachii and the skin of arm.

Below, diagram of the brachial plexus of left side.