The brachial plexus is formed by the anterior primary rami of C5 through T1 and provides sensory and motor innervation of the upper extremity. The brachial plexus is divided, proximally to distally, into rami/roots, trunks, divisions, cords, and terminal branches. The trunks can be found within the posterior triangle of the neck, between the anterior and middle scalene muscles. The brachial plexus, along with the axillary artery, can be considered as a large neurovascular bundle that travels in the axilla to supply the upper extremity.