Final answer:
The brachial plexus is formed from spinal nerves C5 to T1 and is organized into five main components: roots, trunks, divisions, cords, and branches, with each serving a role in the innervation of the arm.
Step-by-step explanation:
The brachial plexus is a complex network of nerves that originates from the lower cervical and upper thoracic spinal nerves, specifically from C5 to T1. It's comprised of five main components, organized in a hierarchical order: roots, trunks, divisions, cords, and branches. The roots are formed by the anterior rami of the spinal nerves C5, C6, C7, C8, and T1. These roots merge to form three trunks: the upper trunk (C5-C6), the middle trunk (C7), and the lower trunk (C8-T1).
The trunks then divide into anterior and posterior divisions. These divisions reorganize to create three cords, named according to their position relative to the axillary artery: lateral, medial, and posterior. Lastly, the cords give rise to multiple branches, which include major peripheral nerves like the axillary, musculocutaneous, radial, median, and ulnar nerves that innervate the muscles and skin of the arm.