Brachial Plexus Anatomy
The brachial plexus is a network of nerves starting from five nerve roots in the upper spine and ending in the five main nerves that control movement and sensation in the arm. It is located near where the neck joins the shoulder, behind the clavicle and between the spine and the upper arm, just distal to the axilla.
These three cords then divide and recombine to form the major nerves of the arm. The posterior cord divides into the axillary and radial nerves. The medial cord divides into the ulnar nerve and one limb of the median nerve. The lateral cord divides into the musculocutaneous nerve and one limb of the median nerve.
This figure illustrates the complex nerve pathways within the brachial plexus. Many small nerves branch off from the brachial plexus. As a result, each of the major nerves of the arm receives input from multiple spinal levels, and each spinal root innervates multiple nerves. Thus, the loss of a portion of nerve fibers at one level can be compensated for by nerve fibers at another level. However, because of the complexity of the nerve pathways within the brachial plexus, surgical repair cannot restore the normal anatomy.