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Cranial Nerves - Iii (Cn Ix, X, Xi & Xii)

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Cranial Nerves - Iii (Cn Ix, X, Xi & Xii) CRANIAL NERVES - III (CN IX, X, XI & XII) DR. SANGEETA KOTRANNAVAR ASSISTANT PROFESSOR DEPT. OF ANATOMY USM KLE IMP BELAGAVI OBJECTIVES • Describe the functional component, nuclei of origin, course, distribution and functional significance of cranial nerves IX, X, XI and XII • Describe the applied anatomy of cranial nerves IX, X, XI and XII overview Relationship of the last four cranial nerves at the base of the skull The last four cranial nerves arise from medulla & leave the skull close together, the glossopharyngeal, vagus & accessory through jugular foramen, and the hypoglossal nerve through the hypoglossal canal Functional components OF CN Afferent Efferent General General somatic afferent fibers General somatic efferent fibers Somatic (GSA): transmit exteroceptive & (GSE): innervate skeletal muscles proprioceptive impulses from skin of somatic origin & muscles to somatic sensory nuclei General General visceral afferent General visceral efferent(GVE): transmit visceral fibers (GVA): transmit motor impulses from general visceral interoceptive impulses motor nuclei &relayed in parasympathetic from the viscera to the ganglions. Postganglionic fibers supply visceral sensory nuclei glands, smooth muscles, vessels & viscera Special Special somatic afferent fibers (SSA): ------------ Somatic transmit sensory impulses from special sense organs eye , nose & ear to brain Special Special visceral afferent fibers Special visceral efferent fibers (SVE): visceral (SVA): transmit sensory transmit motor impulses from the impulses from special sense brain to skeletal muscles derived from taste (tounge) to the brain pharyngeal arches : include muscles of mastication, face, pharynx & larynx Cranial Nerve Nuclei in Brainstem: Schematic picture Functional components OF CN GLOSSOPHARYNGEAL NERVE • Glossopharyngeal nerve is the 9th cranial nerve. • It is a mixed nerve, i.e., composed of both the motor and sensory fibres, but predominantly it is sensory. • It derives its name from the fact that it provides sensory innervation to the tongue and pharynx. • Nerve of 3rd branchial arch NUCLEI OF GLOSSOPHARYNGEAL NERVE Functional components and nuclei of the glossopharyngeal nerve FUNCTIONAL COMPONENTS OF GLOSSOPHARYNGEAL NERVE 1. Special visceral efferent (SVE) fibres: • They arise from nucleus ambiguus. • They supply the stylopharyngeus muscle (from brachial arch so special) 2. General visceral efferent (GVE) fibres: • They are preganglionic parasympathetic fibres and arise from the inferior salivatory nucleus & relay in otic ganglion. • They supply the secretomotor fibres to the parotid gland. 3. Special visceral afferent (SVA) fibres: • They carry taste sensations from the posterior 1/3rd of tongue including vallate papillae and terminate in the nucleus tractus solitarius. 4. General visceral afferent (GVA) fibres: • They carry general sensations of pain, touch, and temperature from the mucous membrane of the pharynx, tonsil, soft palate, and posterior 1/3rd of tongue & terminate in the dorsal nucleus of the vagus. Course and Relations • It arises from the upper part of lateral aspect of the medulla between the olive & inferior cerebellar peduncle by 3-4 rootlets. • Rootlets unite to form a single trunk, runs forward & laterally to leave the cranial cavity by passing through the anterior compartment of the jugular foramen • It passes through smaller superior ganglion lies within & larger inferior ganglion lies just below the jugular foramen & contains cell bodies of most of the sensory fibers of the nerve. • From foramen, nerve passes downward & forward between internal carotid artery (ICA) & internal jugular vein. • It then proceeds between internal & external carotid arteries deep to styloid process to reach the lateral aspect of the stylopharyngeus which it supplies. OVERVIEW OF GLOSSOPHARYNGEAL NERVE Branches of CN IX • Observe the modality of each branch & relate it to function of nerve Branches of CN IX 1. Tympanic branch (Jacobson’s nerve): forms tympanic plexus (over the promontory of the middle ear) the lesser petrosal nerve, carries secretomotor fibers to otic ganglion supplies parotid gland via auriculotemporal N BRANCHES OF GLOSSOPHARYNGEAL NERVE IN TYMPANIC CAVITY • It leaves the inferior ganglion and enters the middle ear through the tympanic canaliculus situated at the bony edge between the jugular foramen and carotid canal. • It forms the tympanic plexus over the promontory of the middle ear. • The tympanic plexus gives off: (a) the lesser petrosal nerve and (b) twigs to tympanic cavity, auditory tube, and mastoid air cells. 2. Carotid nerve (nerve of Herring): Sensory branch to carotid sinus and carotid body. It serves as an afferent limb for baro-receptor & chemo-receptor reflexes from the carotid sinus & carotid body to regulate the heart rate and respiration, respectively. 3. Pharyngeal branch: Carries sensation from mucous membrane of pharynx. It joins the pharyngeal branches of the vagus and the cervical sympathetic chain to form the pharyngeal plexus on the middle constrictor of the pharynx. 4.Tonsillar branches: They supply the mucous membrane of tonsil and palate. 5. Lingual branches: They supply the posterior one-third of the tongue and vallate papillae and convey taste and general sensations. 6. Branch to stylopharyngeus: It is the only motor branch that supplies stylopharyngeus muscle. Applied anatomy 1. Lesions of glossopharyngeal nerve: complete lesion of the glossopharyngeal nerve results in: (a) Loss of taste and general sensations over the posterior one-third of the tongue, (b) Loss of general sensation of pharynx, tonsils & post.1/3rd of tongue leads to difficulty in swallowing, (c) the loss of the salivation from the parotid gland, and (d) the unilateral loss of the gag reflex OF CN 9 VAGUS NERVE VAGUS NERVE • Vagus nerve is the 10th cranial nerve. • It is a mixed nerve, i.e., composed of both the motor and sensory fibres but predominantly it is motor. • It is the longest and most widely distributed cranial nerve. • It is so called because of its extensive vague course and distribution. • It is a vagrant or wandering nerve. • Its field of distribution extends beyond the head and neck to the thorax and abdomen. • It conveys most of the efferent fibres of the cranial part of the parasympathetic outflow and distributes the fibres of an cranial part of the accessory nerve. NUCLEI OF VAGUS NERVE Nuclei and Functional components of vagus nerve Efferents Afferents Functional components and nuclei of the vagus nerve 1. Special visceral efferent fibres: supply the muscles of palate, pharynx, and larynx (brachial muscles). They arise from nucleus ambiguus. 2. General visceral efferent fibres: arise from the dorsal nucleus of vagus, and provide parasympathetic innervation to heart, bronchial tree, and most of the GIT. 3. Special visceral afferent fibres: carry taste sensations from the posteriormost part of the tongue and epiglottis and terminate in the nucleus tractus solitarius. 4. General visceral afferent fibres: carry general sensations from the mucous membrane of pharynx, larynx, trachea, esophagus, and thoracic and abdominal viscera and terminate in the nucleus tractus solitarius and some in the dorsal nucleus of the vagus. 5. General somatic afferent fibres: carry general sensations from skin of the auricle and terminate in the nucleus of the spinal tract of the trigeminal nerve. Course and Relations of vagus • vagus nerve arises from the lateral aspect of the medulla between olive & inferior cerebellar peduncle by about 10 rootlets below & in line of rootlets of the CN 9. • These nerve rootlets unite to form the nerve trunk which runs laterally, crosses the jugular tubercle, and leaves the cranial cavity by passing through the middle part of the jugular foramen • A smaller superior ganglion lies within & larger inferior (nodose) ganglion lies just below the jugular foramen. • Cranial root of CN 11 joins below inf. Jugular vein. • Runs vertically downward within the carotid sheath in the neck first between the internal jugular vein and internal carotid artery • At the root of the neck, the Right nerve enters the thorax. • Right vagus nerve enters the thorax by crossing in front & winds round the right subclavian artery • Left vagus nerve enters the thorax by passing between the left common carotid & left subclavian arteries, then winds around the arch of aorta. VISCERAL AND SENSORY DISTRIBUTION OF VAGUS NERVE BRANCHES OF VAGUS NERVE Branches and Distribution 1. Meningeal branch: • Arises from superior ganglion • It supply - dura mater of posterior cranial fossa. 2. Auricular branch (Arnold’s nerve or Alderman’s nerve): • Arises from the superior ganglion • It supplies - floor of the meatus and the tympanic membrane. • Stimulation of this nerve, as in syringing of the ear, may cause reflex coughing (ear cough), vomiting, and even cardiac arrest. 3. Pharyngeal branch: • Takes part in the formation of pharyngeal plexus. • supplies: all the muscles of pharynx except the stylopharyngeus, (which is supplied by CN 9) • supplies: all the muscles of soft palate except the tensor palati (which is supplied by CN V3 through the nerve to medial pterygoid). 4. Branches to carotid body: • Arises from the inferior ganglion & innervates carotid body & sinus. 5. Superior laryngeal nerve (nerve of 4th arch): • External laryngeal nerve – supplies cricothyroid muscle • Internal laryngeal nerve (sensory) passes thro’ thyrohyoid membrane & sensory to mucous membrane above vocal cord 7. Recurrent laryngeal nerve (nerve of 6th arch)
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