CRANIAL NERVES

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CONTENTS

• Introduction• Nerve supply – cranial nerves1. Olfactory2. Optic3. Occulomotor4. Trochlear5. Trigeminal• Opthalmic• Maxillary• mandibular6. Abducent7. Facial8. Vestibulo – cochlear9. Glossopharyngeal10. Vagus11. Accessory12. Hypoglossal

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INTRODUCTION

• Head , neck and face are very important organs for

dentistry.

• Because sensory organs , glands are located in this area.

• The innervation of working field is completely related to

cranial nerves.

• Cranial nerves are important because not only they are

related to cranial cavity but they play a vital role to supply

the structures in the oral cavity.

• Nerve supply of a particular organ is an important aspect in

the study of that organ.

• Any abnormality in the structure may be because of nerve. 3

INTRODUCTION

• Hence it is very important to know the detail structure ,

course and anatomy of the nerve , structures supplied by

the nerve to complete evaluation of our working field.

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NERVE SUPPLY

CRANIAL NERVES

• Nerves those exit from the cranial cavity through openings in the cranium.

• 12 pairs of cranial nerves.

• They are named and numbered in the sequence according to their

attachment to brain and superior spinal cord.

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I - Olfactory

II - Optic

III - Occulomotor

IV - Trochlear

V - Trigeminal

VI - Abducent

VII - Facial

VIII - Vestibulo -

cochlear

IX -

Glossopharyngeal

X - Vagus

XI - Accessory

XII - Hypoglossal

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I. OLFACTORY

• Special sensory

• Cells of origin : Olfactory epithelium

• Cranial exit : Foramina in cribriform plate of ethmoid bone

• Main action : Smell from - nasal mucosa of roof of each nasal cavity

superior sides of nasal septum and

superior concha

• Applied anatomy : destruction of olfactory nerves results in loss of sense of

smell ( anosmia )

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II. OPTIC

• Special sensory

• Cells of origin : Retina (ganglion cells)

• Cranial exit : Optic canal

• Main action : Vision from retina

• Applied anatomy : injury to nerve results in blindness on the same side.

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III. OCCULOMOTOR

• Two functional components

SOMATIC MOTOR

• Cells of origin : Occulomotor nucleus

• Cranial exit : Superior orbital fissure

• Main action : 1. Motor innervation to superior , inferior and medial recti ,

inferior oblique and levator palpebrea superioris

muscles

2. Raises upper eyelid

3. Turns eyeball superiorly , inferiorly and medially

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VISCERAL MOTOR

• Cells of origin : Presynaptic – Midbrain

Postsynaptic : Ciliary ganglion

• Cranial exit : Superior orbital fissure

• Main action : 1. Parasympathetic innervation to sphincter pupillae and ciliary

muscles

2. Constricts pupil

3. Accommodates lens of eyeball

• Applied anatomy : complete or total paralysis of nerve causes –

• Ptosis ( drooping of the upper eyelid )

• Dilatation of the pupil

• Slight proptosis ( forward projection of the eye )

• Diplopia ( double vision )

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IV. TROCHLEAR• Functional component : Somatic motor

• Cells of origin : Trochlear nucleus

• Cranial exit : Superior orbital fissure

• Main action : Motor to superior oblique , which assists in eyeball

inferolaterally

• Applied anatomy : when nerve damaged , diplopia occurs on looking

downwards.

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V. TRIGEMINAL• Largest cranial nerve

• Nerve contains : Sensory fibers

Motor fibers

• Afferent fibers – Sensory fibers ( portio major )

• Efferent fibers – Motor fibers ( portio minor )

• General somatic afferent fibers convey exteroceptive and proprioceptive

impulses.

• Exteroceptive impulses ( Touch , pain and thermal )

Transmitted from skin of the face and forehead and mucous

membrane of nasal cavities and floor of the mouth , teeth , anterior 2/3 rd

of tongue , extensive portion of cranial dura.

• Proprioceptive impulses ( Deep pressure and movement )

Conveyed from teeth , periodontium , hard palate , TMJ

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• Also convey afferent fibers from stretch receptors in muscles of

mastication.

• Special visceral efferent fibers innervate muscles of mastication , tensor

tympani , tensor veli palatini , muscles of eye , facial muscles

• Nerve is attached to lateral part of pons by two roots : Motor and Sensory

• Two roots then enter in middle cranial fossa.

SENSORY ROOT

• Fibers of root arise from seminular ganglion.

• Ganglion is developed from neural crest.

• It is located in Meckel’s cavity.

• Crescent shaped

• Contains unipolar neurons.

• Neurons forms central and peripheral processes. 16

• Peripheral – Form opthalmic , maxillary and mandibular division of nerve.

• Central – Form sensory root of nerve.

- branches leave ganglion and pons , back and enter the pons and

divide into ascending and descending fibers.

- fibers convey light touch , tactile touch , tactile discrimination ,

sense

of position and passive movement

- ascending fibers terminates in upper sensory nucleus (main

nucleus

of nerve)

- upper (main) nucleus give rise to dorsal trigeminotalmic tract.

- spinal nucleus give rise to ventral trigeminothalmic tract.

- ventral fibers convey pain and temperature from entire

trigeminal area.

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MOTOR ROOT

• Consist of fibers which originate in motor nucleus.

• Fibers supply the muscles of mastication.

• So , often nerve is called as masticatory nerve.

MESENCEPHALIC ROOT

• Consist of afferent fibers that accompany the fibers of motor root.

• Entering the pons , fibers ascend to mesencephalic nucleus.

• Nucleus serves as afferent station – receive proprioceptive impulses from -

TMJ , periodontal membrane , maxillary and mandibular teeth ,

hard

palate.

• Also receive afferent impulses from stretch receptors in muscles of

mastication.

• These fibers are connected with control of biting force of jaws.

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DIVISIONS OF TRIGEMINAL NERVE

Three large nerves proceed from convex border of semilunar ganglion.

OPTHALMIC NERVE ( V1 )

MAXILLARY NERVE ( V2 )

MANDIBULAR NERVE ( V3 )

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1. OPTHALMIC NERVE ( V1 )

• First division

• Smallest division

• General sensory

• Cells of origin : Trigeminal ganglion

• Cells of termination : Main , spinal and mesencephalic nucleus of trigeminal nerve.

• Cranial exit – Superior orbital fissure

• Fibers passes sensory impulses from :

Scalp

Skin of forehead

Upper eyelid, lining the frontal sinus

Lining of ethmoid cells

Skin of the lateral angle of the eye

Sclera of the eyeball and conjuctiva

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• Also give communication branches to occulomotor , trochlear and

abducent cranial nerve.

• As it passes forward from cavernous sinus , it gives three branches.

a. LACRIMAL

b. FRONTAL

c. NASOCILLIARY

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a. LACRIMAL

• Smallest

• Passes into the orbit at the lateral angle of superior orbital fissure.

• Then courses anterolaterally to reach lacrimal gland.

• Supplies sensory fibers to lacrimal gland and adjacent conjuctiva.

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b. FRONTAL

• Largest

• Direct continuation of opthalmic nerve

• Enters the orbit through superior orbital fissure

• At about middle of the orbit , nerve divides into two branches :

SUPRAORBITAL SUPRATROCHLEAR

- Largest - Smallest

- Supply – Skin of the upper eyelid - Supply – Skin of upper

eyelid

- the forehead - lower

medial portion

- anterior scalp region to of head

vertex of skull24

c. NASOCILLIARY

• Enters the orbit through superior orbital fissure.

• Branches are divide into those arising in the orbit , in the nasal cavity and

on the face

BRANCHES ARISING IN THE ORBIT

BRANCHES ARISING IN THE NASAL CAVITY

BRANCHES ARISING ON THE FACE

i) Long root of ciliary ganglion – Eyeball

ii) Long ciliary nerves – Iris , cornea

iii) Posterior ethemoid nerve – mucous membrane lining of posterior ethemoidal cells

- sphenoid sinusiv) Anterior ethemoidal nerves –

mucous membrane of anterior ethemoidal cells

- frontal sinusIn upper part of nasal cavity it divides

Internal nasal External nasalBranches branches- Medial or - Skin over tip septal branches and ala of - Lateral branches the nose Ant nasal wall Nasal concha

Branches arise in the nasal cavity to supply mucous membrane lining of the cavity

Branches supply sensory fibers to-Skin of the medial parts of both eyelids-Lacrimal sac-Lacrimal coruncle-Terminal fibers supply the skin over the side of the bridges of nose

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• AUTONOMIC GANGLIAON ASSOCIATED WITH OPTHALMIC NERVE

CILIARY GANGLION

• Lies in the posterior part of the orbital cavity.

• Ganglion has three roots –

A. MOTOR OR SHORT ( PREGANGLIONIC , PARASYMPATHETIC ) ROOT

• Fibers arise from cells in the nucleus of Edinger-Westfal.

• Preganglionic fibers synopse with post-ganglionic fibers , whose neurons form

short ciliary nerve – innervates the sphincter pupillae and ciliary muscles of iris.

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B. SENSORY OR LONG ( POSTGANGLIONIC , SYMPATHETIC ) ROOT

• Fibers derived from nasociliary nerve.

• Root also carries postganglionic fibers of superior cervical sympathetic

ganglion.

• They join nasociliary nerve and to innervate radial fibers of dialator pupillae

muscle in the iris

C. SYMPATHETIC ROOT

• Fibers come from sensory root of nasociliary nerve.

• Short ciliary nerves emerges from anterior border of ciliary ganglion.

• Fibers of nerve contains sensory , sympathetic and parasympathetic fibers.

• SENSORY : Afferent from all parts of eyeball and conjuctiva.

• SYMPATHETIC : Postganglionic fibers pass to radial fibers of dilator pupil muscle

( dilation of pupil )

• PARASYMPATHETIC : Postganglionic fibers innervates the circular muscle fibers

of the iris ( constriction of pupil )

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2. MAXILLARY NERVE ( V2 )

• Entirely sensory

• Originates at the middle of the semilunar ganglion and continue forward in

the lower part of the cavernous sinus.

• Passes through the foramen rotundum , through which it leaves the cranial

fossa and enters the pterigopalatine fossa.

• Then it enters the superior orbital fissure to pass into the orbital cavity.

• Turns laterally , in a groove on the orbital surface of the maxilla , called

infraorbital groove.

• Nerve transmits sensory ( afferent ) impulses from lower eyelid , side of

the nose and upper lip.

• Nerve is sensory to –

- all maxillary teeth and their gingiva

- mucous membrane of most of the nasal cavity

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- Hard and soft palate region

- Part of the tonsillar region

- From the region of the pharynx near the opening of the auditary tube.

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BRANCHES OF THE MAXILLARY NERVE

• Nerve gives off branches in four region :

I) BRANCHES GIVEN OFF IN THE MIDDLE CRANIAL FOSSA

Middle meningeal nerve , passes with middle meningeal artery to

supply dura and sensory fibers.

II) BRANCHES IN THE PTERYGOPALATINE FOSSA

A) Zygomatic nerve

Passes anteriorly and laterally through inferior orbital fissure into

the orbit and divide into two parts :

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i) Zygomaticofacial nerve

Supplies to the skin over the prominences of zygomatic bone.

ii) Zygomaticotemporal nerve

Supplies to the skin over the anterior temporal fossa region.

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B) PTERYGOPALATINE ( SPHENOPALATINE ) NERVES

• Two short nerve trunks that unite at the pterygopalatine ganlion and are then

redistributed into several branches.

• Majority of the fibers are somatic afferent fibers.

• Branches are divided into three groups :

i) Orbital branches

Supply to – periosteum of the orbit

- mucous membrane of the part of the posterior ethemoid cells

- sphenoid sinus

ii) Nasal branches

• In nasal cavity , the branches divide into :

a) Posterior superior lateral nasal branches

Supply to the mucous membrane of the nasal septum and posterior ethemoid cells.

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b) Medial or septal branch

Supplies the mucous membrane over the vomer .

iii) Palatine branches

• Branches descend in the pterygoid canal , where it divide into :

a) Greater or anterior palatine nerve

• Emerges on the hard palate

• Pass through greater palatine foramen

• Supplies the major part of the hard palate and the palatine gingivae.

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b) Middle palatine nerve

• Emerges from lesser palatine foramen

• Supplies the mucous membrane of the soft palate

c) Posterior palatine fibers

• Emerges from lesser palatine foramen

• Supplies to the tonsillar area

C) POSTERIOR SUPERIOR ALVEOLAR BRANCHES

• Two or three branches leave the maxillary division just before it enters the

inferior orbital fissure.

• Pass downward and continue on posterior surface of maxilla.

• An internal branch opens on the posterior surface of maxilla.

• In the bone , the nerve passes downward to the posterior wall of the

maxillary sinus to supply to the mucous membrane of the sinus.

• Also it supplies the maxillary molars and their gingivae.35

• In the depth of the socket , some fibers pass to supply periodontal

membranes.

• Pulpal fibers pass through apical foramina of roots of molar teeth to supply

dental pulps.

III) BRANCHES IN THE INFRAORBITAL GROOVE AND CANAL

• Nerve in the infraorbital groove and canal is known as the infraorbital nerve.

• From groove several fibers divide and descend.

A) Middle superior alveolar nerve

• Branches within the mucous membrane of maxillary sinus.

• In some cases nerve leaves the infraorbital nerve in posterior part of the

infraorbital canal and passes downward and anterior to supply maxillary

bicuspids.

• In other cases , nerve leaves the main trunk in the infraorbital canal near the

infraorbital foramen and passes downward in the anterior wall of the sinus.36

B) Anterior superior alveolar nerve

• Descends from infraorbital nerve just inside the infraorbital foramen.

• Supplies the roots of central and lateral incisors and cuspids.

• Also supplies the mucous membrane of the anterior part of the maxillary

sinus and labial gingivae of the incisors and cuspids.

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IV) TERMINAL BRANCHES ON THE FACE

• When infraorbital nerve emerge from the

Infraorbital foramen on the front of the maxilla

it divides into three branches :

A) Inferior palpebral branches

Pass upward and supplies the skin of the

lower eyelid and its conjuctiva.

B) External / lateral nasal branches

Supplies the skin of the side of the nose

C) Superior labial branches

Supplies the skin and mucous membrane of the

upper lip 38

• AUTONOMIC GANLION ASSOCIATED WITH THE MAXILLARY NERVE

SPHENOPALATINE GANGLION

• Associated with the great superficial petrosal nerve.

• Contains cell bodies of afferent taste fibers.

• Lies deep in pterygopalatine fossa.

• Branches from the ganglion :

A) Orbital branches

• Afferent in nature

• Supply the mucous membrane of the posterior ethmoid cells and the

sphenoid sinus.

B) Nasal branches

• Divided into two groups :

i) Posterior superior lateral nerves

Innervates the mucosa over the posterior part of the nasal concha.39

ii) Nasopalatine nerve

Supplies the mucous membrane of maxilla.

C) Palatine branches

• From ganglion , branches descends in the pterygopalatine fossa and canal

and divides into :

i) Greater / anterior palatine nerve

Supplies the major part of the mucous membrane of the hard palate

and palatal gingivae.

ii) Middle palatine nerve

Supplies mucous membrane of the soft palate.

iii) Posterior palatine nerves

Supplies the mucous membrane of the tonsillar area.

D) Pharyngeal branches

supplies mucous membrane of the nasopharynx.40

3. MANDIBULAR NERVE ( V3 )

• Largest of the three divisions

• Union of large sensory ( afferent ) bundles of fibers and small motor ( efferent )

bundle of fibers.

• Sensory fibers :

• peripheral extensions of unipolar cells in the semilunar ganglion.

• Fibers are distributed to : the dura, skin, mucous membrane of the chin , cheek

and lower lip

- the external ear region

- parotid gland

- temporomandibular articulation

- the scalp over the region of the temporal bone

- lower teeth and their gingivae

- anterior 2/3rd of the tongue 41

• Motor fibers :

• Fibers are derived from the cells in the medulla oblangata.

• When sensory root leaves the semilunar ganglion , motor root joins it.

• Two roots pass side by side upto foramen ovale.

• Leaving the foramen ovale , the two roots unite to form a short single

trunk.

• Branches are divided into two groups :

A) BRANCHES FROM THE UNDIVIDED NERVE

i) Nervus spinosus

Supplies the dura of the middle cranial fossa and the mastoid cells.

ii) Nerve to internal pterygoid muscle

A branch of the motor root passes to supply internal pterygoid muscle.

B) BRANCHES OF THE DIVIDED NERVE

Below the level of the undivided part , trunk seperates into two parts :42

i) Anterior division

• Smaller

• Receives sensory and motor fibers that supply :

the muscles of mastication

the skin and mucous membrane of the cheek

the buccal gingivae

lower molars

• Then it passes downward and forward , where it divides

Branch Supply

1. Pterygoid nerve Motor nerve supply to external pterygoid muscle

2. Massetter nerve Enters the deep side of massetter muscle to supply it

3. Nerves to temporal muscle a. Anterior deep temporal nerve

Ends in the deep part of the anterior portion of the temporal muscle

b. Posterior deep temporal nerve Posterior portion of temporal muscle43

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4. Buccal nerve

• At about level of the occlusal plane of mandibular seond and third molars ,

it divides into several branches.

• Sends fibers to the mucous membrane of the cheek region.

• Some other fibers pass into the retromolar triangle.

• Supplies sensory fibers to the buccal gingivae of mandibular molars and

mucous membrane of buccal vestibule.

ii) Posterior division

• Mainly sensory but also carries some motor components.

• Divides into :

1. Auriculotemporal nerve

2. Lingual nerve

3. Inferior alveolar nerves45

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1. Auriculotemporal nerve

• Arises by a medial and lateral root

• Roots unite behind the middle meningeal artery just below foramen

spinosum.

• United nerve passes posteriorly , deep to the external pterygoid muscle ,

and then between the sphenomandibular ligament and the neck of the

condyle of the mandible.

• Branches :1. Parotid branches Gives off sensory , secretory and vasomotor fibers to the gland

2. Articular branches Sensory inervation to the TMJ

3. Auricular branches Sensory fibers supplying skin of the helix and tragus

4. Meatal branches Supplies the skin lining of the meatus and the tympanic membrane

5. Terminal branches Scalp over the temporal region47

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2. Lingual nerve

• Smaller

• Passes medially to the external pterygoid muscle.

• Then it descends and lies between internal pterygoid muscle and ramus of

the mandible in the pterygomandibular space.

• In the pterygomandibular space , nerve lies parallel to the inferior alveolar

nerve.

• Then passes deep to reach the side of the base of the tongue.

• Passes sensory innervation from :

- mucous membrane covering the anterior 2/3rd of tongue

- mucous membrane of the floor of the mouth and of the lingual side of

the

mandibular gingivae

- from submandibular and sublingual glands and their ducts49

• Also convey special sense of taste from the anterior 2/3rd of tongue.

3. Inferior alveolar nerve

• Largest

• Passes downward on the medial side of the external petrygoid muscle and

ramus.

• On medial side of ramus in the pterygomandibular space , it enters the

mandibular foramen.

• In the inferior alveolar canal it gives off branches to mandibular teeth as apical

fibers to supply dental pulps and some fibers to periodontal membrane.

• As nerve reaches to mental foramen . It divides into two terminal branches.

• Mental nerve : transmits sensory fibers to the skin of the chin and lower lip and

mucous membrane lining the lower lip.

• Incisive branch : forms a fine incisive plexus that supplies the cuspid tooth and

incisor teeth. 50

AUTONOMIC GANGLIA ASSOCIATED WITH THE MANDIBULAR NERVE

• Two ganglia are associated :

A) Submandibular ganglion

• Small ovoid body

• It is suspended by two nerves from the lingual nerve.

• Parasympathetic fibers are preganglionic

• They course within the intermediate nerve and the facial canal and group

together to form the quarda tympani nerve.

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B) Otic ganglion

• Flattened ovoid body

• Two main roots :

1) Parasympathetic preganglionic fibers

• Arise in the inferior salivatory nucleus

• The lesser petrosal nerve is the parasympathetic root of otic ganglion.

• In the otic ganglion , parasympathetic fibers join the auriculotemporal

nerve to go to the parotid gland.

2) Sympathetic nerve

• Root is made up of postganglionic fibers that originated in the superior

cervical sympathetic ganglion.

• Fibers pass with parasympathetic fibers to join to the auriculotemporal

nerve and continue to the parotid gland.52

• APPLIED ANATOMY

• Because of the sensory distribution of the trigeminal nerve , headache is

common symptom in involvement of nose ( common cold ) , paranasal air

sinuses ( sinusitis ) , teeth ( infections ).

• Trigeminal neuralgia : an extremely painful condition

Trauma to face, facial fractures, and tumours involves the peripheral

branches resulting in anesthesia to light, touch and temperature changes

over the area supplied by injured branch.

• Lingual nerve damage during extraction of lower 3rd molar.

• Care should be taken during surgeries involving premolar areas as they

can cause damage to the mental nerve & result in loss of sensation in chin

region.

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V. ABDUCENT • Functional component – Somatic motor

• Cells of origin – Abducent nucleus

• Cranial exit – Superior orbital fissure

• Main action – Motor to superior oblique that assist in turning eyeball

inferolaterally.

• Applied anatomy : paralysis of nerve results in squint and diplopia.

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VI. FACIAL• It is the nerve of the second branchial arch.

• Functional component –

a) Special visceral efferent ( branchial motor ) – to muscles responsible

for facial expressions

b) General visceral efferent – to fibres are secretomotor to salivary

glands , lacrimal gland and glands of nose , palate and pharynx

c) Special visceral afferent – fibers carry taste sensations from the

anterior 2/3rd of tongue and from the palate

d) General somatic afferent – fibers innervatess a part of the skin of the

ear

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BRANCHES :

A. Within the facial canal

1. Greater petrosal nerve

• Supplies the lacrimal gland and mucosal glands of the nose , palate and

pharynx

2. The nerve to the stapedius

• Arises opposite of the middle ear and supplies the stapedius muscle

3. The chorda tympani nerve

• Secretomotor fibers to supply the submandibular and sublingual salivary

gland

• Taste fibers from anterior 2/3rd of the tongue

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B. As it exit from the stylomastoid foramen

1. Posterior auricular

• Supplies auricularis posterior , occipitalis and the intrinsic muscles on the back of the auricle.

2. Diagastric

• Supplies the posterior belly of diagastric

3. Stylohyoid

• Arise with the diagastric branch and supplies the stylohyoid muscle.

C. Terminal branches ithin the parotid gland

1. Temporal

• Cross the zygomatic arch and supplies – the auricularis anterior

- the auricularis superior

- the intrinsic muscles on the lateral side of the ear

- the frontalis

- the orbicularis occuli

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2. Zygomatic

• Run across the zygomatic bone and supply the orbicularis oculi

3. Buccal

• Two in number

• Upper buccal branch runs above the parotid duct

• Lower buccal branch runs below the parotid duct

• Both supplies the muscles in the viscinity.

4. Mandibular

• Runs below the angle of the mandible.

• Crosses the body of the mandible and supplies muscles of the lower lip and

chin.

5. Cervical

• Emerges from the apex of the parotid gland and supplies platysma.59

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D. Communicating branches

• Motor nerves of the three branchial arches communicate with each other.

• Facial nerve also communicates with adjacent cranial and spinal nerves.

GANGLIA ASSOCIATED WITH FACIAL NERVE

1) The geniculate ganglion

• Sensory ganglion

• Peripheral processes of unipolar neurons of the ganglion are the taste

fibers in the nerve.

2) The submandibular ganglion

• Parasympathetic ganglion.

• Station for secretomotor fibers to the submandibular and sublingual

salivary glands.

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3) Pterygopalatine ( Sphenopalatine ) ganglion

• Parasympathetic ganglion

• Serves as a relay station for secretomotor fibers to the lacrimal gland and

to the mucous glands to the nose , paranasal sinuses , palate and pharynx.

• APPLIED ANATOMY

• Facial nerve paralysis

• Paralysis of facial muscles on affected side

and loss of taste sensation.

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VIII. VESTIBULOCOCHLEAR• Fibers arise from the hearing and equilibrium apparatus of the inner ear,

pass through the internal acoustic meatus, and enter the brainstem at the

pons-medulla border.

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• Two branches :

a) Vestibular nerve

• Concerned with equilibrium.

• Nuclei – the four vestibular nuclei : superior , Inferior , medial , lateral

• Cranial exit : Internal acoustic meatus

• Main action : vestibular sensation from semicircular ducts , utricle and

saccule related to position and movement of head.

b) Cochlear nerve

• Concerned with hearing.

• Nuclei : the dorsal and ventral cochlear nuclei

• Cranial exit : Internal acoustic meatus

• Main action : Hearing from spinal organ

• Applied anatomy : injury to nerve causes hearing defect.64

IX. GLOSSOPHARYNGEAL

• Nerve of the third branchial arch.

• Fibers emerge from the medulla, leave the skull via the jugular foramen.

• Mixed nerve with motor and sensory functions.

• Motor – innervates part of the tongue and pharynx, and provides motor

fibers to the parotid salivary gland

• Sensory – fibers conduct taste and general sensory impulses from the

tongue and pharynx.

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• BRANCHES –

1. Tympanic nerve

• Disributes branches to the middle ear , the auditary tube , the mastoid antrum

and air cells.

2. Carotid branch

• Supplies the carotid sinus and carotid body.

3. Pharyngeal branches

• Take part in the formation of the pharyngeal plexus.

• Fibers are distributed to the mucous membrane of the pharynx.

4. Muscular branch

• Supplies the stylopharyngeus

5. Tonsillar branches

• Supplies the tonsil

6. Lingual branches

• Carry taste and general sensations from posterior 1/3rd of the tongue

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• Applied anatomy

• Clinical testing - on clicking the posterior wall of pharynx , there is reflex

contraction of throat muscles. It is absent in nerve paralysis.

• Also taste sensations are lost on posterior 1/3rd of tongue.

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X. VAGUS

• It is so called because of its extensive ( vague ) course through the head ,

neck , thorax and abdomen.

• Fibers emerge from the medulla via the jugular foramen.

• The vagus is a mixed nerve.

• Most motor fibers are parasympathetic fibers to the heart, lungs, and visceral

organs.

• Its sensory function is in taste.

• Nuclei : motor – nucleus ambiguus

dorsal vagal nucleus

• Sensory – solitary trigeminal nucleus

- spinal trigeminal nucleus68

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• Branches in the head and neck

a) In the jugular foramen

1. Meningeal branch

• Supply to the concha and root of the auricle

posterior half of the external auditary meatus

the tympanic membrane

2. Auricular branch

• Sensation from auricle , external acoustic meatus

b) The branches arising in the neck

1. Pharyngeal branch

• Supplies muscles of the pharynx and palate ( except tensor palati )

2. Carotid branch

• Supplies the carotid body70

3. Superior laryngeal nerve

i) External ii)Internal laryngeal

Laryngeal nerve nerve

- supplies - supplies mucous membrane of larynx above the

level

Cricothyroid muscle of vocal folds

4. Right recurrent laryngeal nerve

• Supplies :

• All intrinsic muscles of larynx , except cricothyroid

• Sensory nerves of larynx below the level of vocal cords

• Cardiac branches to the deep cardiac plexus

• the trachea and oesophagus

• To the inferior constrictor

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5. Cardiac

• Divided as superior and inferior

• Out of four branches ( two on each side ) left inferior branch goes to the

superficial cardiac plexus.

• Other three nerves go to the deep cardiac plexus.

APPLIED ANATOMY

• Clinical testing – by comparing palatal arches of two sides.

• On paralysed side , no arching and uvula is pulled to normal side.

• Paralysis of nerve causes – nasal regurgitation of swallowed liquids.

- nasal twang in voice

- hoarseness of voice

• Irritation of auricular branch may cause persistent cough.72

XI. ACCESSSORY• Two roots :

• cranial root - emerging from the medulla

• spinal root - arising from the superior region of the spinal cord.

• Cells of origin – accessory nucleus of spinal cord

• Cranial exit – jugular foramen

• Primarily a motor nerve.

• Supplies fibers to the larynx, pharynx, and soft palate

Innervates the trapezius and sternocleidomastoid, which move the head and

neck

• APPLIED ANATOMY

• Clinical testing – by asking patient to turn the face to the opposite side

against resistant.

• Irritation of the nerve may produce torticollis. 73

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XII. HYPOGLOSSAL

• Fibers arise from the medulla.

• Functional component – somatic motor

• Cells of origin – hypoglossal nucleus

• Cranial exit - hypoglossal canal

• Supply all the intrinsic and extrinsic muscles of the tongue

• APPLIED ANATOMY

• Clinical testing : by asking the patient to protrude his tongue ( deviation to

paralysed site )

• Lesion produces paralysis on affected side

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CONCLUSION

• study of the nerve supply of orofacial region helps to get

knowledge of different structures which are directly or

indirectly related to oral cavity.

• Nerves specially trigeminal and facial , without a thorough

knowledge of it, its anatomy & physiology, diagnostic and

therapeutic procedures will be not be useful.

• Also detailed study of bony structures and relation to

nerves location is important for the local anaesthesia.

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REFERENCES

• B.D. Chaurasia’s Human Anatomy , Vol Three – Head , Neck

and Brain – Third ed

• Monheim’s Local Anesthesia And Pain Control In Dental

Practice , C. Richard Bennett , 7th Ed

• Grant’s Atlas Of Anatomy , Anne M.R. , Arthur F. Dalley – 7th

ed.

• Handbook of Local Anesthesia , Stanley F. Malamed – 5th ed

• Textbook of Oral Medicine , Anil Ghom

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