Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Facial Nerve Lecture PPT
FACIAL NERVE
Functional components
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Motor ( SVE ) - muscles of facial expression ,
stapedius , stylohyoid
posterior belly of digastric
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Secretomotor ( GVE ) - lacrimal gland , glands in m.m. of nose, PNS , palate & nasopharynx
submandibular , sublingual and other minor salivary glands ,
mucosal glands in oral cavity
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Sensory ( SVA ) - taste from anterior 2/3 of tongue
from floor of oral cavity & palate
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Sensory ( GSA ) - from EAC ( ext. auditory canal )
Facial nerve nuclei
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Main motor nucleus ( SVE )
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Parasympathetic nuclei ( Superior salivatory nucleus & lacrimatory nucleus - GVE )
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Sensory nuclei ( Nucleus of Tractus Solitarius - SVA ,
Spinal part of Sensory nucleus of CN V - GSA )
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Main motor nucleus
> lies deep in the reticular formation of lower part of pons
> supplies muscles derived from 2nd branchial arch
> supranuclear connections - IMPORTANT
Upper part of nucleus receives corticonuclear fibres from both cerebral hemispheres
Lower part of nucleus receives only contralateral corticonuclear fibres
These connections have important bearing on clinical presentation of lesions affecting
facial nerve .
These connections explain voluntary control of facial muscles .
Another INVOLUNTARY pathway exists ?
It is separate & controls mimetic / emotional changes in facial expression .
It forms part of reticular formation .
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Parasympathetic nuclei
> lie posterolateral to main motor nucleus
> they are superior salivatory nucleus
& lacrimal nucleus
Neurons of the 2 nuclei seem to be intermingled with each other and exact location of these
nuclei in humans are uncertain
> receives afferent fibers from -
1. hypothalamus through autonomic descending pathways
2. taste fibers ascending from NTS
> lacrimal nucleus receives afferent fibers from
1. hypothalamus for emotional responses
2. sensory nuclei of CN V for reflex lacrimation .
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Sensory nucleui - NTS ( SVA) , Spinal nucleus of CN V ( GSA )
> upper part of NTS (nucleus of tractus solitarius ) lies close to motor nucleus
> taste pathway -
Receptors ( taste buds )
1st order neuron ( geniculate ganglia )
NTS
2nd order neuron
cross the median plane and ascend to
VPMN ( ventral posteromedial nucleus )of opposite thalamus
& to a number of hypothalamic nuclei -
3rd order neuron
from thalamus pass through internal capsule & corona-radiata to end in taste area of the cortex in
lower part of post central gyrus ( insular cortex ) .
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Sensory nuclei cont'd .....
> sGSA fibers from
concha of EAC &
retroauricular groove region
will reach the
sensory nucleus of CN V
(after entering brainstem) &
then run with the CN V
Branches of facial nerve
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Greater superficial petrosal nerve
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Nerve to stapedius
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Chorda tympani
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Communicating branch
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Posterior auricular nerve
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Muscular branches
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Peripheral branches -
> 2 divisions entering the parotid are temporofacial / temporozygomatic
& cervicofacial
they form a network of nerves within parotid ( pes anserinus /goose foot )
the plexus gives of five / five group of branches
these branches leave the parotid and diverge into there area of distribution
branches are ?
1. temporal
2. zygomatic
3. buccal
4. mandibular
5. cervical
> they supply all muscles of facial expression
Course of facial nerve
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Motor root
Starting from motor nucleus first travels posteriorly around the medial side of abducent nucleus &
then loops around the nucleus of CNVI coming lateral to it . This loop of facial nerve lies in the floor
of IV th ventricle & produces an elevation in the ventricle called facial colliculus .
After looping around nucleus of CN VI it passes anteriorly to emerge from brainstem .
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Sensory root ( nervus intermedius / nerve of Wrisberg ) made of
1. central processes of unipolar cells of geniculate ganglion
2. parasympathetic fibers ?
efferent preganglionic parasympathetic fibers from superior salivatory and lacrimal nuclei .
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The course of the facial nerve can be divided into
> intracranial - 24mm ( 5-12mm in IAC )
> intratemporal - 28 ? 30 mm , facial (fallopian) canal ;
labyrinthine segment - 3-5mm
first genu ( geniculate ganglion) -
tympanic segment 8-11mm
second genu
mastoid segment 12 ? 20mm
stylomastoid foramen
> extratemporal portions
This post was last modified on 30 November 2021