Brachial plexus

Overview
The brachial plexus is an arrangement of nerve fibres, running from the spine, specifically from above the fifth cervical vertebra to underneath the first thoracic vertebra (C5-T1). It proceeds through the neck, the axilla (armpit region) and into the arm.

Function
The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve and an area of skin near the axilla innervated by the intercostobrachialis nerve.

This function may be impaired by tumor growth of the Apical region of either Lung.

Therefore, brachial plexus lesions can lead to severe functional impairment.

Path
One can remember the order of brachial plexus elements by way of the mnemonic, "Read The Damn Cadaver Book" - Roots, Trunks, Divisions, Cords, Branches or - Roots, Trunks, Divisions, Cords, Collateral/Pre-terminal Branches, and (Terminal) Branches.


 * The five roots are the five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck.


 * These roots merge to form three trunks:
 * "superior" or "upper" (C5-C6)
 * "middle" (C7)
 * "inferior" or "lower" (C8-T1)


 * Each trunk then splits in two, to form six divisions:
 * anterior division of the superior, middle, and inferior trunks
 * posterior division of the superior, middle, and inferior trunks


 * These six divisions will regroup to become the three cords. The cords are named by their position in respect to the axillary artery.
 * The posterior cord is formed from the three posterior divisions of the trunks (C5-T1)
 * The lateral cord is the anterior divisions from the upper and middle trunks (C5-C7)
 * The medial cord is simply a continuation of the lower trunk (C8-T1)


 * The branches are listed below. Most branch off of the cords, but a few branch (indicated in italics) directly off of earlier structures. The five in bold are considered "terminal branches".