Cranial Nerves Sanjaya Adikari Department of Anatomy

Cranial Nerves

Sanjaya AdikariDepartment of Anatomy

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

1. Position of nucleus

2. Emerging point from brain stem

3. Intracranial course

4. Point of exit from the cranial cavity

5. Extracranial course

6. 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

endodermectoderm

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

SMVM

VS

BM

SS

Brain stem

SpSGSS

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

VSGSS

SS

IIIIVVIXII

BM

VVIIIXXXI

VM

IIIVIIIXX

VIIIXX

VVIIIXX

VIII

Functional components of cranial nerves

Somatic Motor

Muscles of the orbit (III, IV, VI)

Muscles of tongue (XII)

IIIIV

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)

SensoryConsists 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 sensoryHearing via VIII (vestibulocochlear nerve)

SM VMVS

BM

GSSSS

VVIIIXXXI

IIIIVVIXII

IIIVIIIXX

VIIIXX

VVIIIXX

VIII

Intracranial course and exit

Sanjaya AdikariDepartment of Anatomy

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 tractAnterior perforatedsubstance

Uncus

Bypass thalamus and goes directly into the taste area

Nerve filaments

Cribriform plate of ethmoid bone

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 bodyof thalamus

Internalcapsule

Optic radiation

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 muscleSphincter pupillae

Ciliary ganglion

Superior division

Inferior division

Sympathetic fromInternal carotid plexus

Parasympathetic fromEW nucleus

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

Oculomotor N (III)

Ventral midbrain

Lateral wallCavernous S

Divide Sup. & Inf.divisions

Sup/infraorbital fissure

Trochlear N (IV)

Dorsalmidbrain

Lateral wallCavernous S

Superior orbital fissure

Abducent N (VI)

BetweenPons & pyramid of medulla

withinCavernous S

Superior orbital fissure

Cavernous sinus

1- Oculomotor N2- Trochlear N3- Abducent N4- Ophthalmic branch of TN

5- Maxillary branch of TN 6- Sympathetic plexus of N7- Internal carotid A8- 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 orderSA fibres

Trigeminal ganglion

Somatic sensory nucleus

Branchial motor nucleus

Foramen ovale

Ophthalmic division

Maxillary division

Lat. Wall ofcavernoussinous

Mandibulardivision

Mandibularnerve(mixed)

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 ofTractus solitarious

Chorda tympaninerve

Taste from anterior tongue

Nervousintermedius

Facial Nerve…cont.

Branchial motornucleus

Nerve to stapedius

Stylomastoid foramen

Pure branchial motor facial nerveSupply muscles of facial expression

Ear drum

VE to submandibular gland and glands on the mouth floor

Greater petrosal nerveSup.

salivarynucleus

Internal acoustic meatus

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 nucleiin pons

Vestibular nucleiin medulla

Glossopharyngeal Nerve (IX)

Branchial motor nucleus (Nucleus ambiguus)

supplies stylopharyngeus muscle

Parasympathetic nucleus (Inferior salivary nucleus)

supplies parotid gland

Sensory nucleiGSS 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

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

Accessory Nerve (XI)

Branchial motor nerve

Cranial root From nucleus ambiguusFibres 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