The brachial plexus is formed by the ventral rami of cervical nerves C5-C8 and thoracic nerve T1. It provides motor innervation to the muscles of the upper limb and sensory innervation to the upper limb. The roots combine to form three trunks, which each divide into anterior and posterior divisions. The divisions then branch out to form the nerves that innervate specific muscles and skin areas of the arm and hand. The brachial plexus travels from the neck, behind the clavicle, and down the arm, surrounding blood vessels along the way.