cranial nerve XI
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accessory nerveA nerve of the neck.
Roots in lateral medulla oblongata and upper spinal cord.
After multiple roots join, the AN divides into internal (cranial) and external (spinal) branches.
Internal branch innervates vagus—palate, pharynx, larynx, thoracic viscera; external branch innervates sternocleidomastoid and trapezius muscles.
AN lesions cause drooping of the shoulder and inability to rotate the head away from the affected side.