Eleventh cranial nerve

Eleventh Cranial Nerve

The eleventh cranial nerve, also known as the accessory nerve.

The eleventh cranial nerve or accessory nerve is a cranial nerve that controls the sternocleidomastoid and trapezius muscles, which are responsible for movements of the head and shoulders. It is unique among the cranial nerves as it originates from both the brain and the spinal cord.

Structure

The eleventh cranial nerve is composed of two parts: the cranial part and the spinal part. The cranial part originates from the medulla oblongata, while the spinal part arises from the upper segments of the spinal cord. These two parts join to form the accessory nerve, which then splits again to innervate the sternocleidomastoid and trapezius muscles.

Function

The accessory nerve is primarily a motor nerve, controlling the movements of the sternocleidomastoid and trapezius muscles. These muscles are involved in various movements of the head and shoulders, including turning the head, shrugging the shoulders, and bending the neck.

Clinical significance

Damage to the eleventh cranial nerve can result in a condition known as accessory nerve palsy, which is characterized by weakness or paralysis of the sternocleidomastoid and trapezius muscles. This can lead to difficulties in moving the head and shoulders, and may also cause the shoulder to droop on the affected side.

See also

• Cranial nerves
• Sternocleidomastoid muscle
• Trapezius muscle