Left Brachial Plexus Anatomy
The brachial plexus is a network of nerves that supplies the axilla, brachium (upper arm), antebrachium (forearm), and hand. It is classified into five different segments: roots, trunks, divisions, cords, and terminal branches. The five roots are comprised of the ventral rami of spinal nerve roots C5-C8 and T1. These nerve roots then merge together to form three trunks. Roots C5-C6 form the superior trunk, C7 forms the middle trunk, and C8-T1 forms the inferior trunk. Each trunk then divides into two divisions (an anterior division, and a posterior division), resulting in six divisions total. These six divisions then merge back together to form three cords- posterior, lateral, and medial. The three posterior divisions merge to form the posterior cord, the anterior divisions from the superior and middle trunks merge to form the lateral cord, and the anterior division of the inferior trunk becomes the medial cord. The three cords then divide one last time to form the terminal branches of the brachial plexus: the musculocutaneous nerve, axillary nerve, radial nerve, median nerve, and ulnar nerve. These terminal branches will then continue on through the upper arm, forearm, and hand, supplying sensory-motor function.