The Cranial Nerves

The Cranial 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

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 Sensory cranial nerves: contain only afferent (sensory) fibers nerves ⅠOlfactory nerve 

  



Motor cranial nerves: contain only efferent (motor) fibers     



ⅡOptic nerve Ⅷ Vestibulocochlear nerve 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 N.

Location of cell body and axon categories

Cranial exitTerminal nuclei

Ⅰ

Olfactory cells (SVA)

Cribrifom Olfactory bulbSmell foramina

Ⅱ

Ganglion cells (SSA)

Optic canalLateral geniculate body

Vision

Internal acoustic meatus

Vestibular nuclei

Equilibriu m

Cochlear nuclei

Hearing

Ⅷ Vestibular ganglion(SSA) Cochlear ganglion (SSA)

Main action

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

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

Vestibulocochlear nerve Vestibular ganglion(SSA) ↘

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

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)

Superior orbital fissure

Motor to superior obliquus

Ⅵ

Nucleus of abducent nerve (GSE)

Superior orbital fissure

Motor to lateral rectus

Ⅺ

Nucleus of accessory nerve (SVE)

Jugular foramen

Motor to sternocleidomastoid and trapezius

Ⅻ Nucleus of hypoglossal Hypoglossal canal nerve( GSE)

Motot to muscles of tongue

Oculomotor nerve 

Components  



Main action － supplies 



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General somatic efferent fibers (GSE) General visceral efferent fibers (GVE) 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

Hypoglossal nerve

Hypoglossal nerve

Oculamotor paralysis

Abducent nerve injury

Mixed cranial nerves

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 Branches  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) 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

Glossopharyngeal nerve Components of fibers(Ⅸ) 







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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) components of fibers 





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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 

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

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