Cranial Nerves Dr.Haythem Ali Alsayigh

12 pairs of cranial nerves III to XII attached to brain stem Their cell bodies form nuclei in the brain stem First cell body of sensory nerves lie out side CNS (form ganglia)

Summary of cranial nerves Aspects to study Position of nucleus Emerging point from brain stem Intracranial course Point of exit from the cranial cavity Extracranial course Distribution

Few terms: Somatic, branchial and visceral

Branchial (Pharyngeal) Arches ectoderm endoderm Core of mesodermal tissue covered by ectoderm and endoderm Each of the arch will have its own bone/cartilage, muscles, nerve and artery

Mandibular branch of trigeminal nerve (V) Facial nerve (VII) Premaxilla, maxilla, zygomatic bone, part of temporal bone and mandible Glossopharyngeal nerve (IX) Superior laryngeal branch of vagus nerve (X) Recurrent laryngeal branch of vagus nerve (X)

Visceral In relation to internal organs Heart Lung Intestines ……………… ……………..

Few hints Nerve A Nerve B

Posterior Somatic sensory Visceral sensory Motor Sensory Visceral motor Somatic motor Spinal cord (thoracic or lumbar) Posterior horn Lateral horn Anterior horn Motor Sensory

Brain stem SpS GSS SS VS VM BM SM

Types of sensations General Visceral sensory Visceral sensory pain, temperature, touch, viration position sense Visceral sensory Special Visceral sensory taste General Somatic sensory pain, temperature, touch, vibration position sense Somatic sensory Special Somatic sensory hearing

SpS SS VS BM SM VM SpS SS VS BM SM VM

III IV V VI VII XII IX X XI III VII IX VII X IX X V VII IX X VIII SS GSS VS VIII SM BM VM VII IX X V VII IX X XI

Functional components of cranial nerves III IV Somatic Motor Muscles of the orbit (III, IV, VI) Muscles of tongue (XII) VI XII

Branchial Motor Muscles of mastication (V) Facial muscles (VII) Pharyngeal and laryngeal muscles (Nucleus ambiguus via IX, X, XI nerves)

Visceral Motor Edinger Westphal nucleus (accessory oculomotor) Salivary nuclei (NI part of VII, IX) Dorsal motor nucleus of vagus (for cardiac muscles, smooth muscles of alimentary tract)

Sensory Visceral sensory with taste Consists of single nuclei for visceral and somatic sensory Visceral sensory with taste Nucleus of tractus solitarious which receives taste fibres from the tongue through VII, IX and sensory from heart, lungs and other viscera through X

General somatic sensory Sensory nucleus of trigeminal nerve extending from the midbrain to the cervical spinal cord

Special somatic sensory Hearing via VIII (vestibulocochlear nerve)

III IV III VI VII XII IX X V VII IX VII X IX XI X V VII IX X VIII SS GSS SS VS VIII BM SM VM VII IX X V VII IX X XI

Intracranial course and exit

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

Functional components General somatic afferent fibers (GSA): transmit exteroceptive and proprioceptive impulses from head and face to somatic sensory nuclei Special somatic afferent fibers (SSA): transmit sensory impulses from special sense organs of vision, equilibrium and hearing to the brain General visceral afferent fibers (GVA): transmit interoceptive impulses from the viscera to the visceral sensory nuclei Special visceral afferent fibers (SVA): transmit sensory impulses from special sense organs of smell and taste to the brain General somatic efferent fibers (GSE): innervate skeletal muscles of eye and tongue Special visceral efferent fibers (SVE): transmit motor impulses from the brain to skeletal muscles derived from brachial (gill) arches of embryo. These include the muscles of mastication, facial expression and swallowing General visceral efferent fibers (GVE): transmit motor impulses from the general visceral motor nuclei and relayed in parasympathetic ganglions. The postganglionic fibers supply cardiac muscles，smooth muscles and glands

Classification of cranial nerves Sensory cranial nerves: contain only afferent (sensory) fibers ⅠOlfactory nerve ⅡOptic nerve Ⅷ Vestibulocochlear nerve Motor cranial nerves: contain only efferent (motor) fibers Ⅲ Oculomotor nerve Ⅳ Trochlear nerve ⅥAbducent nerve Ⅺ Accessory nerv Ⅻ Hypoglossal nerve Mixed nerves: contain both sensory and motor fibers--- ⅤTrigeminal nerve, Ⅶ Facial nerve, ⅨGlossopharyngeal nerve ⅩVagus nerve

Sensory cranial nerves Location of cell body and axon categories Cranial exit Terminal nuclei Main action Ⅰ Olfactory cells (SVA) Cribrifom foramina Olfactory bulb Smell Ⅱ Ganglion cells (SSA) Optic canal Lateral geniculate body Vision Ⅷ Vestibular ganglion(SSA) Internal acoustic meatus Vestibular nuclei Equilibrium Cochlear ganglion (SSA) Cochlear nuclei Hearing

Motor cranial nerves N. Nucleus of origin and axon categories Cranial exit Main action Ⅲ Nucleus of oculomotor (GSE) Superior orbital fissure Motot to superior, inferior and medial recti; inferior obliquus; levator palpebrae superioris Accessory nucleus of oculomotor (GVE) Parasympathetic to sphincter pupillea and ciliary muscl Ⅳ Nucleus of trochlear nerve (GSE) Motor to superior obliquus Ⅵ Nucleus of abducent nerve (GSE) Motor to lateral rectus Ⅺ Nucleus of accessory nerve (SVE) Jugular foramen Motor to sternocleidomastoid and trapezius Ⅻ Nucleus of hypoglossal nerve( GSE) Hypoglossal canal Motot to muscles of tongue

Optic canal (II) Superior orbital fissure (III, IV, V1, VI) Foramen rotundum (V2) Foramen ovale (V3) Foramen spinosum Foramen lacerum Internal acoustic meatus (VII, VIII) Jugular foramen (IX, X, XI) Hypoglossal canal (XII)

Olfactory Nerve (I) Anterior perforated substance Olfactory tract Uncus Olfactory bulb Nerve filaments Cribriform plate of ethmoid bone Bypass thalamus and goes directly into the taste area

Olfactory nerve Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb

Optic Nerve (II) T N

Optic Nerve (II) Optic nerve Optic chiasma Optic tract Optic radiation Superior colliculus (body reflexes) Pretectal nucleus (pupillary reflexes) Internal capsule Lateral geniculate body of thalamus

Optic nerve Ganglion cell (SSA) → Optic canal → Lateral geniculate body

Oculomotor Nerve (III) Somatic motor nucleus Visceral motor nucleus (Edinger westphal nucleus) Nerve emerges from ventral aspect of midbrain travel’s in the lateral wall of the cavernous sinus

Oculomotor Nerve… cont. Levator palpabrae superioris Dilator pupillae Sympathetic from Internal carotid plexus Superior division Superior rectus Medial rectus, inferior rectus, inferior oblique Inferior division Parasympathetic from EW nucleus Ciliary muscle Sphincter pupillae Ciliary ganglion

Oculomotor nerve Oculomotor nerve Components Main action－supplies General somatic efferent fibers (GSE) General visceral efferent fibers (GVE) Main action－supplies Superior, inferior and medial recti; inferior obliquus; levator palpebrae superioris Sphincter pupillea and ciliary muscle Ciliary ganglion: lies between optic nerve and lateral rectus Oculomotor nerve

Accessory nerve Abducent nerve

Trochlear Nerve (IV) Somatic motor nucleus Emerges from the dorsal aspect of midbrain Travels in the lateral wall of the cavernous sinus Supplies the superior oblique muscle

Abducens Nerve (VI) Somatic motor nucleus Nucleus lies in lower pons near midline Emerge between pons and pyramid of medulla Travels through the cavernous sinus Supply the lateral rectus muscle

Oculamotor paralysis Abducent nerve injury

Oculomotor N (III) Trochlear N (IV) Abducent N (VI) Ventral midbrain Lateral wall Cavernous S Divide Sup. & Inf. divisions Sup/infraorbital fissure Trochlear N (IV) Dorsal midbrain Lateral wall Cavernous S Superior orbital fissure Abducent N (VI) Between Pons & pyramid of medulla within Cavernous S Superior orbital fissure

Cavernous sinus 1- Oculomotor N 2- Trochlear N 3- Abducent N 4- Ophthalmic branch of TN 5- Maxillary branch of TN 6- Sympathetic plexus of N 7- Internal carotid A 8- Pituitary gland

LR6(SO4)3

Trigeminal nerve (V) Branchial motor nucleus Somatic sensory nucleus Emerge from the ventral aspect of pons Sensory and motor roots emerge separately

Trigeminal nerve… cont. Somatic sensory nucleus Trigeminal ganglion Cell bodies of 1st order SA fibres Ophthalmic division Lat. Wall of cavernous sinous Maxillary division Mandibulardivision Mandibularnerve (mixed) Branchial motor nucleus Foramen ovale

Trigeminal nerve Components of fibers SVE fibers: originate from motor nucleus of trigeminal nerve, and supply masticatory muscles GSA fibers: transmit facial sensation to sensory nuclei of trigeminal nerve, the GSA fibers have their cell bodies in trigeminal ganglion, which lies on the apex of petrous part of temporal bone

Branches Ophthalmic nerve (Ⅴ1, sensory) leave the skull through the superior orbital fissure, to enter orbital cavity Frontal nerve Supratrochlear nerve Supraorbital nerve Lacrimal nerve Nasociliary nerve

Distribution: Sensation from cerebral dura mater Visual organ Mucosa of nose Skin above the eye and back of nose

Maxillary nerve (Ⅴ2, sensory) Leave skull through foramen rotundum Branches Infraorbital nerve Zygomatic nerve Superior alveolar nerve Pterygopalatine nerve

Distribution: Sensation from cerebral dura mater Maxillary teeth Mucosa of nose and mouth Skin between eye and mouth

Mandibular nerve (Ⅴ3, mixed) Leave the skull through the foramen ovale to enter the infratemporal fossa Branches Auriculotemporal nerve Buccal nerve Lingual nerve Inferior alveolar nerve Nerve of masticatory muscles

Distribution: Sensation from cerebral dura mater Teeth and gum of lower jaw Mucosa of floor of mouth Anterior 2/3 of tongue Skin of auricular and temporal regions and below the mouth Motor to masticatory muscles, mylohyoid, and anterior belly of digastric

Facial Nerve (VII) Visceral motor nucleus (Superior salivary nucleus) Branchial motor nucleus Visceral motor nucleus (Superior salivary nucleus) Taste sensory nucleus (Tractus solitarius) Main facial nerve and the nervous intermedius parts emerge from the cerebellopontine angle

Facial Nerve…cont. Internal acoustic meatus Geniculate ganglion (taste 1st order cell bodies) Nucleus of Tractus solitarious Chorda tympani nerve Taste from anterior tongue Nervous intermedius Branchial motor nucleus VE to submandibular gland and glands on the mouth floor Greater petrosal nerve Sup. salivary nucleus Nerve to stapedius Ear drum Stylomastoid foramen Pure branchial motor facial nerve Supply muscles of facial expression

Facial nerve (Ⅶ) Components of fibers SVE fibers originate from nucleus of facial nerve, and supply facial muscles GVE fibers derived from superior salivatory nucleus and relayed in pterygopalatine ganglion and submandibular ganglion. The postganglionic fibers supply lacrimal, submandibular and sublingual glands SVA fiber from taste buds of anterior two-thirds of tongue which cell bodies are in the geniculate ganglion of the facial nerve and end by synapsing with cells of nucleus of solitary tract GSA fibers from skin of external ear

Course: leaves skull through internal acoustic meatus, facial canal and stylomastoid foramen, it then enters parotid gland where it divides into five branches which supply facial muscles

Branches within the facial canal Chorda tympani : joins lingual branch of mandibular nerve To taste buds on anterior two-thirds of tongue Relayed in submandibular ganglion, the postganglionic fibers supply submandibular and sublingual glands

Greater petrosal nerve: GVE fibers pass to pterygopalatine ganglion and there relayed through the zygomatic and lacrimal nerves to lacrimal gland Stapedial nerve : to stapedius

Branches outside of facial canal Temporal Zygomatic Buccal Marginal mandibular Cervical

Pterygopalatine ganglion: lies in pterygopalatine fossa under maxillary nerve Submandibular ganglion : lies between lingual nerve and submandibular gland

Injury to the facial nerve

Vestibulocochlear Nerve (VIII) Internal acoustic meatus Spiral ganglion of cochlea Cochlear nuclei in pons Cochlear nerve Hair cells of spiral organ Vestibular ganglion Vestibular nuclei in medulla Cerebellopontine angle Vestibular nerve Hair cells of utricle, saccule and semilunar canals

Vestibulocochlear nerve Vestibular ganglion(SSA) ↘ ↗ Vestibular nuclei Internal acoustic meatus Cochlear ganglion (SSA) ↗ ↘ Cochlear nuclei

Glossopharyngeal Nerve (IX) Branchial motor nucleus (Nucleus ambiguus) supplies stylopharyngeus muscle Parasympathetic nucleus (Inferior salivary nucleus) supplies parotid gland Sensory nuclei GSS from posterior tongue goes to sensory nucleus of trigeminal nerve Taste from the posterior tongue goes to the tractus solitarius VS from baroreceptors go to nucleus of tractus solitarius

Glossopharyngeal nerve (Ⅸ) Components of fibers SVE fibers: originate from nucleus ambiguus, and supply stylopharygeus GVE fibers: arise from inferior salivatory nucleus and ralyed in otic ganglion, the postganglionic fibers supply parotid gland SVA fibers: arise from the cells of inferior ganglion, the central processes of these cells terminate in nucleus of solitary tract, the peripheral processes supply the taste buds on posterior third of tongue GVA fibers: visceral sensation from mucosa of posterior third of tongue, pharynx, auditory tube and tympanic cavity, carotid sinus and glomus, and end by synapsing with cells of nucleus of solitary tract GSA fibers: sensation from skin of posterior surface of auricle and

Course: leaves the skull via jugular foramen Branches Lingual branches : to taste buds and mucosa of posterior third of tongue Pharyngeal branches : take part in forming the pharyngeal plexus Tympanic nerve : GVE fibers via tympanic and lesser petrosal nerves to otic ganglion, with postganglionic fibers via auriculotemporal (Ⅴ3) to parotid gland Carotid sinus branch : innervations to both carotid sinus and glomus Others: tonsillar and stylophayngeal branches Otic ganglion : situated just below foramen ovale

Vagus Nerve (X) Branchial motor nucleus (Nucleus ambiguus) supplies pharyngeal constrictors Visceral motor nucleus (Dorsal motor nucleus of vagus) supplies muscles of heart, bronchi, oesophagus, stomach and intestines Visceral sensory nucleus VS from larynx, heart, lung… goes to nucleus of tractus solitarius GSS goes to sensory nucleus of trigeminal nerve

Vagus nerve (Ⅹ) components of fibers GVE fibers: originate from dorsal nucleus of vagus nerve, synapse in parasympathetic ganglion, short postganglionic fibers innervate cardiac muscles, smooth muscles and glands of viscera SVE fibers: originate from ambiguus, to muscles of pharynx and larynx GVA fibers: carry impulse from viscera in neck, thoracic and abdominal cavity to nucleus of solitary tract GSA fiber: sensation from auricle, external acoustic meatus and cerebral dura mater

Course Right vagus nerve Exits the skull from jugular foramen Descends in the neck in carotid sheath between internal (or common) carotid artery and internal jugular vein Right vagus nerve Enter thoracic inlet on right side of trachea Travels downward posterior to right brachiocephalic vein and superior vena cava Passes posterior to right lung root 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

Left vagus nerve Enter thoracic inlet between left common carotid and left subclavian arteries, posterior to left brachiocephalic vein Crosses aortic arch where left recurrent laryngeal nerve branches off Passes posterior to left lung root 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

Cervical cardiac branches : descending to terminate in cardiac plexus Branches in neck Superior laryngeal nerve: passes down side of pharynx and given rise to Internal branch, which pierces thyrohyoid membrane to innervates mucous membrane of larynx above fissure of glottis External branch, which innervates cricothyroid Cervical cardiac branches : descending to terminate in cardiac plexus Others: auricular, pharyngeal and meningeal branches

Superior laryngeal nerve Internal branch External branch

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

Branches in abdomen Anterior and posterior gastric branches Run close to lesser curvature and innervate anterior and posterior surfaces of stomach As far as pyloric antrum to fan out into branches in a way like the digits of a crow’s foot to supply pyloric part Hepatic branches: join hepatic plexus and then supply liver and gallbladder Celiac branches: send branches to celiac plexus to be distributed with sympathetic fibers to liver, pancreas, spleen, kidneys, intestine as far as left colic flexure

Accessory Nerve (XI) Branchial motor nerve Somatic motor nerve Cranial root From nucleus ambiguus Fibres in the cranial root join the vagus nerve Somatic motor nerve Spinal root Anterior horn cells of upper 5-6 cervical spinal segments Fibres in the spinal root supply sternocleidomastoid and trapezius muscles

Hypoglossal Nerve (XII) Somatic motor nerve Leaves cranial cavity through the hypoglossal canal Supplies all muscles (intrinsic and extrinsic) of tongue except palatoglossus

GSA VE BE BA

GSA BE BA VE

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