The Brachial Plexus – this network of nerves extends from the neck into the axilla and supplies motor, sensory, and sympathetic nerve fibers to the upper limb. The brachial plexus is formed by the union of the ventral rami of Nerves C5 – T1. The ventral rami that form the brachial plexus lie between the anterior and middle scalene muscles.
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Begin with the Pectoral girdle with the pectoral muscles removed.
Add the Ventral Primary Rami of C5 and C6.
C5 and C6 unite to form the superior trunk.
Add the Ventral Primary Rami of C7.
C7 continues as the middle trunk.
Add the Ventral Primary Rami of C8 and T1.
C8 and T1 unite at the neck of the first rib to form an inferior trunk. The inferior trunk lies on the first rib posterior to the subclavian artery.
Each of the three trunks then divide into anterior and posterior divisions posterior to the clavicle. These divisions are of fundamental significance because the anterior divisions supply the flexor (anterior) parts and the posterior divisions supply extensor (posterior) parts of the upper limb.
