XI-Accessory
The Accessory nerve is composed purely of motor fibres. The accessory nerve has a spinal part in addition to the cranial part.
Innervation
- Sternomastoid and trapezius muscle
Function
- Movement of the head and shoulders
Anatomy
Cranial part
The cranial part originates from the caudal part of the nucelus ambiguus in the medulla and emerges from the lateral medulla via a series of rootlets. The fibres join the vagus nerve when reach the level of the jugular foramen.
Spinal part
The spinal part starts from motor neurones in the ventral horn of the grey matter at spinal levels C1-C5. The axons of the nerves leave by rootlets from lateral side of the spinal cord and enter the skull through the foramen magnum. Fibres from the spinal part go on to innervate the sternomastoid and trapezius muscles.