Cranial Nerves

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

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

endoderm

ectoderm

• Branchial

Premaxilla, maxilla, zygomatic bone, part of temporal bone and mandible
Mandibular branch of trigeminal nerve (V)
Facial nerve (VII)
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 horn

Lateral horn
Anterior horn

Motor

Sensory

Motor

Sensory

Posterior

Spinal cord (thoracic or lumbar)
Somatic sensory
Visceral sensory
Visceral motor
Somatic motor









SM
VM
VS
BM
SS
Brain stem
SpS
GSS

• Types of sensations

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


SM
VM
VS
BM
SS
SpS

SM
VM
VS
BM
SpS
SS





SM
VS
GSS
SS
III
IV
VI
XII


BM

V
VII
IX
X
XI
VM
III
VII
IX
X

VII
IX
X

V
VII
IX
X


VIII

Functional components of cranial nerves

Somatic Motor

Muscles of the orbit (III, IV, VI)

Muscles of tongue (XII)




III
IV
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

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)








SM
VM
VS
BM
GSS
SS
V
VII
IX
X
XI

III
IV
VI
XII

III
VII
IX
X


VII
IX
X

V
VII
IX
X

VIII

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
• N.
• 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)
• 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 nerve( GSE)
• Hypoglossal canal
• Motot to muscles of tongue

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)

Optic canal

(II)


Olfactory Nerve (I)

Olfactory bulb

Olfactory tract

Anterior perforated

substance

Uncus

Bypass thalamus and goes directly into the taste area
Nerve filaments

Cribriform plate of

ethmoid bone

Olfactory nerve

Olfactory mucosa (SVA)→ Cribriform foramina → Olfactory bulb





Optic Nerve (II)


T
N
T

Optic Nerve (II)

Optic nerve

Optic chiasma

Optic tract
Superior colliculus
(body reflexes)
Pretectal nucleus
(pupillary reflexes)

Lateral geniculate body

of thalamus
Internal
capsule
Optic
radiation


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

Superior rectus
Medial rectus, inferior rectus, inferior oblique

Ciliary muscle

Sphincter pupillae
Ciliary ganglion

Superior division

Inferior division
Sympathetic from
Internal carotid plexus

Parasympathetic from

EW nucleus

Oculomotor nerve

Components
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

Abducent nerve

Accessory 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)

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.

Cell bodies of 1st order
SA fibres
Trigeminal ganglion

Somatic sensory

nucleus
Branchial motor
nucleus


Foramen ovale

Ophthalmic division

Maxillary division

Lat. Wall of

cavernous
sinous
Mandibulardivision

Mandibularnerve

(mixed)

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)

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

Geniculate ganglion

(taste 1st order cell bodies)

Nucleus of

Tractus solitarious
Chorda tympani
nerve

Taste from anterior tongue

Nervous
intermedius

Facial Nerve…cont.

Branchial motor
nucleus
Nerve to stapedius

Stylomastoid foramen

Pure branchial motor facial nerve
Supply muscles of facial expression

Ear drum

VE to submandibular gland and glands on the mouth floor
Greater petrosal nerve

Sup. salivary

nucleus

Internal acoustic meatus

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)
Cochlear nerve
Vestibular nerve
Hair cells of spiral organ
Hair cells of utricle, saccule and semilunar canals

Spiral ganglion of cochlea

Vestibular ganglion

Internal acoustic meatus

Cerebellopontine angle

Cochlear nuclei

in pons

Vestibular nuclei

in medulla

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

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

External branch

Internal 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

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














BE
VE
BA
GSA





BE
VE
BA
GSA

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