The Spinal Accessory Nerve is the eleventh cranial nerve, primarily responsible for controlling certain neck and shoulder muscles. It has two parts: the cranial part, which helps with swallowing by innervating muscles in the throat, and the spinal part, which innervates the sternocleidomastoid and trapezius muscles, aiding in head movement and shoulder elevation. This nerve originates from the spinal cord and the brainstem, traveling upward to reach its target muscles. Damage to the spinal accessory nerve can lead to weakness in neck rotation and shoulder elevation, affecting daily activities and overall mobility.