Accessory nerve

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Accessory Nerve

The Accessory Nerve (pronounced: əkˈses(ə)rē nərv), also known as the Eleventh Cranial Nerve or Spinal Accessory Nerve, is a cranial nerve that controls the sternocleidomastoid and trapezius muscles, which are responsible for movements of the head and shoulders.

Etymology

The term "Accessory" is derived from the Latin word "accessorius" meaning additional. This nerve was named as such because it was considered an additional nerve, not originally counted among the primary cranial nerves.

Anatomy

The Accessory Nerve originates from the medulla oblongata and the upper segments of the spinal cord. It is unique among the cranial nerves as it has both a cranial and a spinal part. The cranial part is often considered a separate nerve, called the Cranial Accessory Nerve, but it is generally accepted that it is part of the Accessory Nerve.

Function

The Accessory Nerve provides motor innervation to the sternocleidomastoid muscle and the trapezius muscle, enabling movements of the head and shoulders. The sternocleidomastoid muscle is involved in rotating the head, while the trapezius muscle moves the scapula and supports the arm.

Clinical Significance

Damage to the Accessory Nerve can result in weakness or paralysis of the sternocleidomastoid and trapezius muscles, leading to difficulties in moving the head and shoulders. This can occur due to surgical procedures in the neck region, trauma, or neurological conditions such as Multiple Sclerosis.

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