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

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

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

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

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

Cranial Nerves

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

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

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

Cranial Nerve XI: Accessory

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

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

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

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

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

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

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

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

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

Cranial Nerve XII: Hypoglossal

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

BRANCHES OF HYPOGLOSSAL NERVE 1 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).

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. 2009. Grant’s Atlas of Anatomy, 12th Edition. Lippincott, Williams & Wilkins, New York.

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