Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Trigeminal Nerve Lecture PPT
Trigeminal nerve
? C N V
? 3 divisions - opthalmic , maxillary , mandibular
? Opthalmic - sensory ( GSA )
cornea , upper eyelid and corresponding part of conjunctiva ,
skin of forehead , scalp , nose and also mucous membrane
of paranasal sinuses & nasal cavity
passes through superior orbital fissure
? Maxillary - sensory ( GSA )
skin of face over maxilla ,
teeth of upper jaw ,
m. m. of nose , maxillary sinus & palate
passes through formen rotundum
? Mandibular division -
Motor ( SVE ) - muscles of mastication ( temporalis ,
masseter, medial and lateral pterygoid )
mylohyoid ,
anterior belly of digastric
tensor veli palatini ,
tensor tympani
Sensory ( GSA ) - skin of cheek ,
skin over mandible & side of head
teeth of lower jaw & TM joint
m.m. of mouth & ant. Part of tongue
opening in skull - foramen ovale
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Largest cranial nerve
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Trigeminal Nerve Nuclei
Sensory nucleus - mesencephalic nucleus
main sensory nucleus
spinal nucleus
Motor nucleus
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Mesencephalic Nucleus
Composed of a column of unipolar nerve cells situated in the lateral part of gray matter around
cerebral aqueduct. It extends inferiorly into the pons as far as the main sensory nucleus .
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Main Sensory Nucleus
Lies in upper part of pons in dorsolateral area of tegmentum of pons, lateral to motor nucleus .
It is continuous below with spinal nucleus.
Contains cell bodies of fibres carrying touch and pressure senses .
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Spinal Nucleus
Is continuous superiorly with main sensory nucleus in the pons and extends inferiorly through the
whole length of medulla oblongata and into upper part of spinal cord as far as second or third
cervical segment . In spinal cord it blends with dorsal horn of spinal grey matter .
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Motor Nucleus
Situated in pons medial to main sensory nucleus
Nuclei of trigeminal nerve
Cut section of pons
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Sensory Components of the Trigeminal Nerve
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Fibers conducting pain , temperature , touch and pressure senses
Sensations of pain, temperature, touch, and pressure from skin of face and mucous membranes
travel along axons whose cell bodies are situated in semilunar/gasserian/trigeminal sensory
ganglion .
The central processes of these cells form large sensory root of trigeminal nerve.
About half fibers divide into ascending and descending branches when they enter pons; remainder
ascend or descend without division .
Ascending branches terminate in main sensory nucleus, and
Descending branches terminate in spinal nucleus.
Sensations of touch and pressure are conveyed by nerve fibers that terminate in main sensory
nucleus.
Sensations of pain and temperature pass to spinal nucleus .
Fibers from ophthalmic division - inferior part of spinal nucleus;
Fibers from maxillary division - middle of spinal nucleus; and
Fibers from mandibular division - superior part of spinal nucleus.
Nuclei of trigeminal nerve
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Fibres carrying proprioceptive impulses
Proprioceptive impulses from muscles of mastication and
from facial and extraocular muscles
are carried by fibers in sensory root of trigeminal nerve that have bypassed semilunar ganglion .
They are peripheral processes of unipolar cells of mesencephalic nucleus .
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Axons of neurons in main sensory and spinal nuclei and central processes of cells in mesencephalic
nucleus now cross median plane and ascend as trigeminal lemniscus ( ventral trigeminothalamic
tract ) ,
some uncrossed fibres ascend as dorsal trigeminothalamic tract
both terminate on
nerve cells of VPMN (ventral posteromedial nucleus ) of thalamus.
Axons of these cells ( VPMN cells ) now travel through internal capsule
to
Postcentral gyrus (areas 3, 1, and 2) of cerebral cortex.
Pathway of sensory fibres
Motor Component of the Trigeminal Nerve
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The motor nucleus receives corticonuclear fibers from both cerebral hemispheres .
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It also receives fibers from
reticular formation,
red nucleus,
tectum, and
medial longitudinal fasciculus.
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In addition, it receives fibers from the mesencephalic nucleus, thereby forming a monosynaptic
reflex arc.
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The cells of motor nucleus give rise to axons that form motor root.
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Motor root supplies
muscles of mastication,
tensor tympani , tensor veli palatini,
mylohyoid and
anterior belly of digastric muscle.
Trigeminal nerve nuclei in the brainstem and their central connections.
Distribution of trigeminal nerve
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Ophthalmic division ( GSA )
Cornea, conjunctiva, and intraocular structures
Mucosa of paranasal sinuses (frontal, sphenoid, and ethmoid)
Mucosa of upper and anterior part of nasal septum and lateral wall of nasal cavity
Lacrimal duct
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Maxillary division ( GSA )
Mucosa of maxillary sinus
Mucosa of posterior part of nasal septum and lower part of nasal cavity
Upper teeth and gum
Hard palate
Soft palate and tonsil
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Mandibular division ( GSA , SVE )
Mucosa of cheek, lower jaw, floor of mouth, tongue
Proprioception from jaw muscles
Lower teeth and gum
Mastoid cells
Muscles derived from 1st pharyngeal arch
Cutaneous distribution
Course of trigeminal nerve
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Motor nucleus ---- motor root --- mandibular division --- foramen ovale ---
infratemporal fossa ---- branches of mandibular division ---
muscles derived from 1st pharyngeal arch
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Sensory nucleus ---- sensory root ----- trigeminal ganglion ----
three divisions of trigeminal nerve ---
branches of the three divisions -----
receptors in area of distribution of the three divisions
This post was last modified on 30 November 2021