anatomy and physiology mcqs

Question #539

The accessory nerve

The accessory nerve is the eleventh cranial nerve and is divided into two separate components.

The cranial accessory nerve arises from the nucleus ambiguus in the brainstem. On exiting the brainstem it travels for a very short distance with the spinal accessory nerve fibres before joining the vagus nerve. It is often considered a part of the vagus nerve rather than as a separate cranial nerve.

The spinal accessory nerve arises from the ventral rami of the cervical spinal cord between C2-4. The rootlets arise from the posterior half of the spinal cord and ascend up into the skull through the foramen magnum. The spinal accessory briefly joins the cranial accessory nerve before they separate again.

The spinal accessory nerve continues out through the jugular foramen anterior to the internal jugular vein. It passes deep to the tip of the styloid process and then deep to the posterior belly of digastric and the occipital artery. It supplies sternocleidomastoid before piercing the muscle and entering the posterior triangle of the neck. The nerve terminates as it innervates trapezius.

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