The Accessory Nerve (XI) is the only cranial nerve that has fibers that enter and leave the skull through different foramina.
The Accessory Nerve (XI):
- Efferent nerves from the brainstem and spinal cord give rise to cranial nerve 11.
- They help to enable phonation and movements of the head and shoulders when they leave the skull through the jugular foramen.
- The accessory nerve is joined by sensory fibers from the cervical plexus, giving its target muscles general sensation.
- The accessory nerve divides into spinal and cranial portions.
What is a foramen?
- An opening that allows the movement of structures from one area to another is called a foramen (plural foramina).
- The term "cranial foramina" refers to the numerous foramina in the base of the skull that carry cranial nerves, blood vessels, and other structures.
- The largest cranial foramen is the foramen magnum.
- It is located in the posterior cranial fossa of the occipital bone and enables the medulla and meninges, vertebral arteries, anterior and posterior spinal arteries, and dural veins to pass through.
- Through the foramen magnum, the spinal division of the accessory nerve ascends to join the cranial division.
- The united nerve then leaves the body through the jugular foramen.
- The petrous portion of the temporal bone forms the jugular foramen anteriorly, while the occipital bone forms it posteriorly.
Thus, the Accessory Nerve (XI) enters through the foramen magnum and leaves through the jugular foramen.
Learn more about "cranial nerves" from here:
https://brainly.com/question/13232548
#SPJ4
