Cranial Nerves IX & X Prof. Mujahid Khan

Objectives: At the end of the lecture, the students should be able to: Describe the component fibers of 9th & 10th cranial nerves List the nuclei of the 9th & 10th nerves in the brain stem Describe the course and relations of the 9th & 10th cranial nerves in the head & neck List the branches of each of these 2 nerves Describe how to test the integrity of these 2 nerves Describe the effect of lesion of any of these 2 nerves

Names of Cranial Nerves Ⅰ Olfactory nerve Ⅱ Optic nerve Ⅲ Oculomotor nerve Ⅳ Trochlear nerve Ⅴ Trigeminal nerve Ⅵ Abducent nerve Ⅶ Facial nerve Ⅷ Vestibulocochlear nerve Ⅸ Glossopharyngeal nerve Ⅹ Vagus nerve Ⅺ Accessory nerve Ⅻ Hypoglossal nerve

Classification of Cranial Nerves Sensory cranial nerves: are composed entirely of afferent (sensory) nerve fibers bringing sensations to the brain Ⅰ Olfactory nerve Ⅱ Optic nerve Ⅷ Vestibulocochlear nerve Motor cranial nerves: are composed entirely of efferent (motor) fibers Ⅲ Oculomotor nerve Ⅳ Trochlear nerve Ⅵ Abducent nerve Ⅺ Accessory nerve Ⅻ Hypoglossal nerve Mixed cranial nerves: possess both sensory and motor fibers Ⅴ Trigeminal nerve Ⅶ Facial nerve Ⅸ Glossopharyngeal nerve Ⅹ Vagus nerve

Cranial Nerves Anatomical origin There are 12 paired cranial nerves The first 2 cranial nerves attach directly to forebrain (frontal lobe), while the rest attach to brain stem 1- Olfactory system is attached to forebrain 2- Optic nerve also is described in visual pathway Cranial nerves 3 - 12 have nuclei (cranial nerve nuclei) in the brain stem

Cranial Nerves 3 & 4- Occulomotor & trochlear nerves are attached to midbrain 5- Trigeminal nerve is attached to antero-lateral surface of pons 6 - 7 & 8- Abducent, Facial & vestibulo-cochlear nerves are lying between pons & medulla oblongata from medial to lateral 9- Hypoglossal nerve is attached to antero-lateral sulcus of medulla oblongata 10, 11 & 12- Glossopharyngeal, vagus & accessory nerves are attached to postero-lateral sulcus of medulla oblongata

Cranial Nerves

Glossopharyngeal (IX) General characteristics of CN IX ● mediates taste (gustation), salivation, and (with CN X and CN XII) swallowing ● mediates input from the carotid sinus, which contains baroreceptors that monitor arterial blood pressure ● mediates input from the carotid body, which contains chemoreceptors that monitor the carbon dioxide and oxygen concentration of the blood

Glossopharyngeal (IX) General characteristics of CN IX ● the nerve of the third pharyngeal arch ● predominantly a sensory nerve ● exits the brainstem (medulla) from the post-olivary sulcus with CN X ● exits the skull via the jugular foramen with CN X and CN XI Branches: Lingual Carotid sinus branch Otic ganglion

Glossopharyngeal (IX) 1. ● innervates the middle ear cavity and part of the external auditory meatus ● has cell bodies in the superior glossopharyngeal ganglion ● projects its central processes to the spinal trigeminal tract and nucleus

Glossopharyngeal (IX) 2. ● innervates structures derived from endoderm (e.g., foregut) ● innervates the mucous membranes of the posterior third of the tongue, tonsil, upper pharynx (soft palate), tympanic cavity, and auditory tube ● innervates the carotid sinus (baroreceptors) and the carotid body (chemoreceptors) ● has cell bodies in the inferior (petrosal) ganglion ● the afferent limb of the gag reflex and the carotid sinus reflex 3. ● innervates the taste buds of the posterior third of the tongue

Glossopharyngeal (IX) 4. ● innervates the stylopharyngeus muscle ● arises from the nucleus ambiguus of the lateral medulla 5. ● a parasympathetic component that innervates the parotid gland ● consists of preganglionic neurons in the inferior salivatory nucleus of the medulla

GLOSSO-PHARYNGEAL NERVE (9TH CRANIAL NERVE ) inf. cerebellar peduncle 1 Nuclei: -Nucleus ambiguus (A) -Nucleus dorsalis (B) -Nucleus solitarius (C) -Inferior salivary nucleus (D) the n. in groove between olive and inf. cerebellar peduncle pons medulla olive tongue 2 3 5 site of hyoglossus m. 7 8 9 4 6 glosso- pharyngeal n. 2 ganglia 1 Course of glosso-pharyngeal nerve (9th cranial nerve)

اسم ورقم المقرر – Course Name and No. 6/10/2019

BRANCHES OF GLOSSOPHARYNGEAL NERVE 1 2 3 4 5 6 tongue ganglia a b c d e f glosso- pharyngeal n. 1.Tympanic nerve 2.  Nerve to stylopharyngeus 3.Pharyngeal branches 4.Carotid nerve 5.Terminal branches

Glossopharyngeal (IX) Clinical correlations: lesions of CN IX 1. Loss of the gag (pharyngeal) reflex (interruption of afferent limb) 2. Loss of the carotid sinus reflex (interruption of the sinus nerve) 3. Loss of taste from the posterior third of the tongue 4. Glossopharyngeal neuralgia

Vagus (X) General characteristics of CN X ● mediates phonation, swallowing (with CN IX and CN XII), elevation of the palate, and taste ● innervates viscera of the neck, thorax and abdomen ● the nerve of the fourth and sixth branchial arches ● exits the brainstem (medulla) from the post-olivary sulcus ● exits the skull via the jugular foramen with CN IX and CN XI

Left Vagus Nerve Course Enter thoracic inlet between left common carotid and left subclavian arteries Crosses the left side of the aortic arch where left recurrent laryngeal nerve branches off Passes posterior to left lung root contributing to the pulmonary plexus Descends on the anterior surface of the esophagus and forms anterior esophageal plexus Forms anterior vagal trunk at esophageal hiatus where it leaves thorax and passes into abdominal cavity, then divides into anterior gastric and hepatic branches

Right Vagus Nerve Course Travels downward anterior to the right subclavian artery and enter thoracic inlet on right side of trachea Passes posterior to right lung root contributing to the pulmonary plexus Then passes on to the posterior surface of esophagus and forms posterior esophageal plexus Forms posterior vagal trunk at esophageal hiatus where it leaves thorax and passes into abdominal cavity, then divides into posterior gastric and celiac branches

Vagus Nerve (Ⅹ) Branches in neck Superior laryngeal nerve: passes down side of pharynx and give rise to Internal branch, which pierces thyrohyoid membrane to innervate mucous membrane of larynx above fissure of glottis External branch, innervates cricothyroid Cervical cardiac branches: descend to terminate in cardiac plexus Others: auricular, pharyngeal and meningeal branches

Vagus Nerve (Ⅹ) Superior laryngeal nerve External branch Internal branch External branch

Vagus Nerve (Ⅹ) Branches in thorax Recurrent laryngeal nerves Right one hooks around right subclavian artery, left one hooks aortic arch Nerves enter larynx posterior to cricothyroid joint, the nerve is now called inferior laryngeal nerve Innervations: laryngeal mucosa below fissure of glottis, all laryngeal muscles except cricothyroid Bronchial and esophageal branches

Vagus (X) 1. ● innervates the infratentorial dura (with C2 and C3) external ear, external auditory meatus, and tympanic membrane ● has cell bodies in the superior (jugular) ganglion ● projects its central processes to the spinal trigeminal tract and nucleus 2. ● innervates the mucous membranes of the pharynx, larynx, esophagus, trachea, and thoracic and abdominal viscera (to the mid-transverse colon) ● has cell bodies in the inferior ganglion

Vagus (X) 3. ● innervates the taste buds over the epiglottis and soft palate ● has cell bodies in the inferior ganglion 4. ● innervates the pharyngeal arch muscles of the larynx and pharynx, striated muscle of the upper esophagus, musculus uvulae, and levator palati and palatoglossus ● arises from the nucleus ambiguus in the lateral medulla ● provides the efferent limb of the gag reflex

Vagus (X) 5. ● innervates the viscera of the neck and the thoracic and abdominal cavities as far as the mid-transverse colon ● consists of preganglionic parasympathetic neurons in the dorsal motor nucleus of the vagus, which project to the intramural ganglia of the viscera

Vagus (X) Clinical correlations: lesions of CN X ● result in the following conditions: 1. Ipsilateral paralysis of the soft palate, pharynx, and larynx leading to dysphonia (hoarseness), dyspnea, dysarthria, and dysphagia 2. Loss of the gag (palatal) reflex 3. Anesthesia of the pharynx and larynx, leading to unilateral loss of the cough reflex 4. Aortic aneurysms and tumors of the neck and thorax ● frequently compress the vagus nerve

X : Vagus Nerve It is mixed nerve, attached lateral to olive of medulla caudal to glossopharyngeal nerve in groove between olive & inferior cerebellar peduncle It receives afferent fibers from: 1-Receptors for general sensation in pharynx, larynx, tympanic membrane, external acoustic meatus 2-Chemoreceptors in aortic bodies and baroreceptors in aortic arch 3-Receptors in thoracic & abdominal viscera

X: Vagus Nerve Fibers 1-Afferent fibers for general sensation: end in sensory nucleus of trigeminal and visceral sensory afferents end in nucleus solitarius 2-Efferent Motor fibers: arise from nucleus ambiguus of medulla to innervate muscles of soft palate, pharynx, larynx to control swallowing and speech 3-Efferent parasympathetic fibers: arise from dorsal nucleus of vagus to supply CVS, RS & GIT

VAGUS NERVE Nuclei : 4 nuclei in the medulla -Nucleus ambiguus (A) 1 2 3 4 5 vagus pharyngeal br. sup. laryngeal carotid br. recurrent laryngeal Nuclei : 4 nuclei in the medulla -Nucleus ambiguus (A) -Nucleus dorsalis (B) -Nucleus solitarius (C) -Spinal tract and nucleus of trigeminal nerve (D) A B C D pyramid olive Inf. cerebellar peduncle medulla vagus n. COURSE OF VAGUS n.

BRANCHES OF VAGUS NERVE 1 3 4 5 8 7 6 S vagus n. 1. Meningeal branch 2. Communicating branches 3. Auricular branch 4. Pharyngeal branch 5 .Superior laryngeal nerve which divides into: a. External laryngeal nerve (motor) b. Internal laryngeal nerve (sensory) 6. Carotid branch 7. Cardiac branches 8. Right recurrent laryngeal nerve R.L.N

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