Spinal root of accessory nerve

Spinal root of accessory nerve is a part of the accessory nerve, also known as the eleventh cranial nerve or simply CN XI. This nerve is primarily responsible for supplying the sternocleidomastoid and trapezius muscles, which are involved in movements of the head and shoulders.

Etymology

The term "accessory" is derived from the Latin word "accessorius", meaning "additional". This is in reference to the nerve's function as an additional or supplementary nerve to the vagus nerve.

Anatomy

The spinal root of the accessory nerve originates from the lateral aspect of the anterior horn cells of the first five segments of the spinal cord. It ascends through the foramen magnum, the large opening at the base of the skull, and then passes through the jugular foramen to exit the skull. It then descends to innervate the sternocleidomastoid and trapezius muscles.

Function

The spinal root of the accessory nerve provides motor innervation to the sternocleidomastoid and trapezius muscles. The sternocleidomastoid muscle is involved in rotating the head to the opposite side and flexing the neck. The trapezius muscle, on the other hand, is involved in moving the scapulae and extending the neck.

Clinical significance

Damage to the spinal root of the accessory nerve can result in weakness or paralysis of the sternocleidomastoid and trapezius muscles. This can lead to difficulties in moving the head and shoulders, and may also cause a drooping shoulder and a winged scapula.

See also

• Cranial nerves
• Accessory nerve
• Sternocleidomastoid muscle
• Trapezius muscle

References

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  Sagittal section of the brain stem

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  Spinal root of accessory nerve