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Accessory nerve

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noun, plural: vagus nerves

The cranial nerve that innervates pharyngeal, trapezius, and sternocleidomastoid muscles


Cranial nerves are paired nerves that emerge from the brain and the brainstem. They supply the motor pathways between organs in the face and the upper body, and account for detecting and processing various sensations. One of the cranial nerves is the accessory nerve, which is also referred to as the eleventh cranial nerve or cranial nerve XI (CN XI).

In humans and other vertebrates, the accessory nerve is a pair of cranial nerves comprised of motor fibers from the spinal cord. It innervates pharyngeal, trapezius, and sternocleidomastoid muscles. Thus, it is primarily associated with controlling the pharynx and the muscles of the upper chest and the shoulders. It is comprised of two parts: the spinal part and the cranial part. The spinal part arises from the ventrolateral part of the first cervical segments of the spinal cord whereas the cranial part arises from the side of the medulla. Together, they form the accessory nerve trunk that splits into two branches: the internal (supplies the muscles of pharynx, larynx, and soft palate) and the external (supplies the sternocleidomastoid and the trapezius muscles) branches.1

Lesions of the eleventh nerve result in the drooping of the shoulder and inability to rotate the head away from the affected side.


  • cranial nerve XI (CN XI)
  • eleventh cranial nerve

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Related term(s):

1 accessory nerve. (n.d.). The American Heritage® Science Dictionary. Retrieved from website [[1]]