1. Prof. Muhammad Mujahid Khan
CRANIAL NERVES XI & XII
Prof. Muhammad Mujahid Khan
اسم ورقم المقرر – Course Name and No.
6/28/2019

2. Objectives:
At the end of the lecture, the students should be able to:
List the nuclei related to the 11th & 12th cranial nerves
Describe the type and location of each nucleus
Describe the emergence, intracranial course and foramina of exit for 11th& 12th cranial nerves
Describe the important relations of both nerves in the neck
Describe the branches and distribution of both nerves
Describe the effects of lesion of accessory and hypoglossal nerves

3. Accessory Nerve
Accessory nerve is a motor nerve that is formed by the union of a cranial and spinal roots
Some books don’t consider it a cranial nerve because it originates as cranial and spinal roots
It mediates head and shoulder movement
اسم ورقم المقرر – Course Name and No.
6/28/2019

4. Cranial Root
The cranial root is formed from the axons of nerve cells of the nucleus ambiguus
The nucleus receives corticonuclear fibers from both cerebral hemispheres
Efferent fibers of the nucleus emerge from the anterior surface of the medulla oblongata between the olive and the inferior cerebellar peduncle
اسم ورقم المقرر – Course Name and No.
6/28/2019

5. Course of Cranial Root
The nerve runs laterally in the posterior cranial fossa and joins the spinal root
The two roots unite together and leave the skull through the jugular foramen
The roots then separate
Cranial root joins the vagus nerve and is distributed in its pharyngeal and recurrent laryngeal branches to the muscles of soft palate, pharynx and larynx
اسم ورقم المقرر – Course Name and No.
6/28/2019

6. Cranial Nerves

7. Spinal Root
The spinal root is formed from axons of nerve cells in the spinal nucleus
This nucleus is situated in the anterior gray column of the spinal cord in the upper five cervical segments
Spinal nucleus is thought to receive corticospinal fibers from both cerebral hemispheres
اسم ورقم المقرر – Course Name and No.
6/28/2019

8. Course of Spinal Root The nerve fibers emerge from the spinal cord
The fibers form the nerve trunk that ascends into the skull through the foramen magnum
The spinal root passes laterally and joins the cranial root as they pass through the jugular foramen
اسم ورقم المقرر – Course Name and No.
6/28/2019

9. Course
After a short distance the spinal root separates from the cranial root
It then runs downward and laterally and enters the deep surface of the sternocleidomastoid muscle and supplies it
It crosses the posterior triangle of the neck and passes beneath the trapezius muscle and supplies it
اسم ورقم المقرر – Course Name and No.
6/28/2019

10. Cranial Nerve XI: Accessory

11. Course
Accessory nerve thus brings about movements of the soft palate, pharynx and larynx
It controls the movements of two large muscles in the neck
اسم ورقم المقرر – Course Name and No.
6/28/2019

12. اسم ورقم المقرر – Course Name and No.
6/28/2019

13. Hypoglossal Nerve Hypoglossal nerve is a motor nerve
It supplies all the intrinsic muscles of the tongue as well as the styloglossus, hyoglossus and the genioglossus muscles
اسم ورقم المقرر – Course Name and No.
6/28/2019

14. Hypoglossal Nerve
Hypoglossal nucleus is situated close to the midline immediately beneath the floor of the lower part of the fourth ventricle
It receives corticonuclear fibers from both cerebral hemispheres
Cells supplying the genioglossus muscle receive fibers from the opposite cerebral hemisphere
اسم ورقم المقرر – Course Name and No.
6/28/2019

15. Hypoglossal Nerve
The hypoglossal nerve fibers pass anteriorly through the medulla oblongata and emerge as a series of roots in the groove between pyramid and the olive
اسم ورقم المقرر – Course Name and No.
6/28/2019

16. اسم ورقم المقرر – Course Name and No.
6/28/2019

17. Course of the Hypoglossal Nerve
The hypoglossal nerve fibers emerge on the anterior surface of the medulla oblongata between the pyramid and the olive
It crosses the posterior cranial fossa and leaves the skull through hypoglossal canal
It passes downward and forward in the neck between the internal carotid artery and internal jugular vein
اسم ورقم المقرر – Course Name and No.
6/28/2019

18. اسم ورقم المقرر – Course Name and No.
6/28/2019

19. Course of the Hypoglossal Nerve
At the posterior belly of the digastric muscle it turns forward and crosses the internal and external carotid arteries and the loop of the lingual artery
It passes deep to the posterior margin of the mylohyoid muscle
The nerve then sends branches to the muscles of the tongue
اسم ورقم المقرر – Course Name and No.
6/28/2019

20. Cranial Nerve XII: Hypoglossal

21. Course of the Hypoglossal Nerve
In the upper part of its course, the hypoglossal nerve is joined by C1 fibers from the cervical plexus
Thus the hypoglossal nerve controls the movements and shape of the tongue
اسم ورقم المقرر – Course Name and No.
6/28/2019

22. BRANCHES OF HYPOGLOSSAL NERVE1 2 3 4
medulla
hypoglossal n.
hypoglossal canal
tongue
hyoglossus m.
thyrohyoid m.
descendens hypoglossi
descendens cervicalis
ansa cervicalis
genio- glossaus
The first cervical (C1) gives a contribution to the hypoglossal nerve which gives the branches of hypoglossal nerve.
1. Descendens hypoglossi (1)
2. Nerve to thyrohyoid (2)
3. Nerve to geniohyoid (3)
4. The pure hypoglossal
nerve fibers supply the intrinsic
and extrinsic muscles of
tongue (4) (except the palatoglossus).

23. References
Clinical Neuroanatomy for Medical Students, Richard S. Snell-6th Edition.
Clinical Neuroanatomy and related neuroscience. M.J.T. FitzGerald, Jean Folan-Curran, Fourth Edition.
Crossman, AR and Neary D, Neuroanatomy: An Illustrated Colour Text.
Haines, DE, Neuroanatomy: An Atlas of Structures, Sections and Systems.
Agur, A. M. R. and A. F. Dalley Grant’s Atlas of Anatomy, 12th Edition. Lippincott, Williams & Wilkins, New York.

24. THE END