Transcript Cranial Nerve VII: The Facial Nerve

The Facial Nerve:
Functional Components and
Anatomy
Brief overview of cranial nerve functional components
•
•
The 12 cranial nerves participate in a total of seven neural functions. Each of
these seven functions is designated by a three letter acronym.
The first letter is either G (General) or S (Special).
– General refers to primitive and/or external structures of the body.
– Special refers to senses unique to the head (taste, olfaction, hearing, vision, and
balance) and to muscles of branchial arch derivatives.
•
The second letter is either S (Somatic) or V (Visceral).
– Somatic refers to non-visceral structures including skin, muscles, tendons, joints,
retina (vision), basilar membrane (hearing), and utricle/saccula (balance).
– Visceral refers to organs of the body cavity, smooth muscle, vessels, and glands.
•
The third letter is either A (Afferent) or E (Efferent).
– Afferent refers to flow of neural information toward the brain (sensation)
– Efferent refers to flow of neural information toward the periphery (motor).
•
Knowledge of the functional components and the deficits that follow damage
to each provides the basis of the thorough neurological exam.
The Seven Functional Components
• GSA – General Somatic Afferent
– Touch, temperature, and pain from non-visceral structures
• GSE – General Somatic Efferent
– Motor to skeletal muscle
• GVA – General Visceral Afferent
– Touch (distention), temperature, and pain from the viscera
• GVE – General Visceral Efferent
– Motor to viscera, smooth muscle, and glands
• SSA – Special Somatic Afferent
– Vision, hearing, and balance
• SSE – Doesn’t exist
• SVA – Special Visceral Afferent
– Taste and olfaction
• SVE – Special Visceral Efferent
– Motor to muscles derived from the branchial arches
The remainder of this tutorial focuses on the
functional nerve components contained within the
facial nerve:
SVE
GVA
SVA
GVE
GSA
These components, either alone or in combination, make up the
facial nerve and its branches. An understanding of these
components can serve as a template for understanding the other
functional components. In addition, an understanding of the facial
nerve and its components can be applied in clinical situations to
help localize a patient’s defect.
Functional Components Within Branches of the
Facial Nerve:
• Greater Superficial Petrosal Nerve (GSPN)
– GVA, GVE, SVA
• Stapedial Nerve
– SVE
• Chorda Tympani Nerve
– GVE, SVA
• Posterior Auricular Nerve
– SVE, GSA
• Facial Nerve (terminal branch)
– SVE
Anatomy of Facial Nerve Branches
• The facial nerve exits the posterior cranial fossa (PCF) at the internal
acoustic meatus.
• Within the internal acoustic meatus the facial nerve enters the facial
canal.
• The first branch of the facial nerve, the greater superficial petrosal nerve
(GSPN) branches from the geniculate ganglion within the genu of the
facial canal and enters the middle cranial fossa by way of the hiatus of
the canal for the GSPN.
• The second branch of the facial nerve, the stapedial nerve, branches
from the descending portion of the facial nerve and enters the middle
ear.
• The third branch of the facial nerve, the chorda tympani nerve, branches
from the descending portion of the facial nerve and enters the middle
ear. Within the middle ear the chorda tympani nerve crosses the medial
surface of the tympanic membrane. It then passes through the
petrotympanic fissure to enter the infratemporal fossa.
• The descending portion of the facial nerve continues into the parotid
region by way of the stylomastoid foramen.
Overview of Facial
Nerve anatomy in
the skull
Hiatus of canal of greater
superficial petrosal nerve
Internal
Acoustic
Meatus
Posterior
Cranial
Fossa (PCF)
Inferior Orbital Fissure
Lacerate foramen
Greater
superficial
Petrosal
nerve
(GSPN)
Facial
canal
Pterygoid
canal
Greater and
lesser palatine
canals
Petrotympanic
fissure
Facial nerve
Stylomastoid
Foramen
Chorda tympani nerve
Facial nerve
Posterior
auricular N.
The facial nerve exits the posterior cranial fossa (PCF) at the internal acoustic
meatus.
Click here to start Animation
Overview of Facial
Nerve anatomy in
the skull
Hiatus of canal of greater
superficial petrosal nerve
Internal
Acoustic
Meatus
Posterior
Cranial
Fossa
Inferior Orbital Fissure
Lacerate foramen
Pterygoid
canal
Greater
superficial
Petrosal
nerve
(GSPN)
Facial
canal
Petrotympanic
fissure
Facial nerve
Stylomastoid
Foramen
Chorda tympani
Facial nerve
Posterior
auricular N.
Within the internal acoustic meatus the facial nerve enters the facial canal.
Click here to start Animation
Greater and
lesser palatine
canals
Overview of Facial
Nerve anatomy in
the skull
Inferior Orbital Fissure
Hiatus of canal of greater
superficial petrosal nerve
Lacerate foramen
Geniculate ganglion
MCF
Internal
Acoustic
Meatus
Posterior
Cranial
Fossa
Pterygoid
canal
Greater
superficial
Petrosal
nerve
(GSPN)
Facial
canal
Greater and
lesser palatine
canals
Petrotympanic
fissure
Facial nerve
Stylomastoid
Foramen
Chorda tympani
Facial nerve
The first branch of the facial nerve, the greater superficial petrosal nerve (GSPN) branches
from the geniculate ganglion within the genu of the facial canal and enters
the middle cranial fossa (MCF) by way of the hiatus of the canal for the GSPN.
Click here to start Animation
Overview of Facial
Nerve anatomy in
the skull
Hiatus of canal of greater
superficial petrosal nerve
Internal
Acoustic
Meatus
Posterior
Cranial
Fossa
Inferior Orbital Fissure
Lacerate foramen
Pterygoid
canal
Greater
superficial
Petrosal
nerve
(GSPN)
Facial
canal
Stapedial N.
Greater and
lesser palatine
canals
Petrotympanic
fissure
Facial nerve
Stylomastoid
Foramen
Chorda tympani
Facial nerve
Posterior
auricular N.
The second branch of the facial nerve, the stapedial nerve, branches from the
descending portion of the facial nerve and enters the middle ear.
Click here to start Animation
Overview of Facial
Nerve anatomy in
the skull
Hiatus of canal of greater
superficial petrosal nerve
Internal
Acoustic
Meatus
Posterior
Cranial
Fossa
Inferior Orbital Fissure
Lacerate foramen
Greater
superficial
Petrosal
nerve
(GSPN)
Facial
canal
Pterygoid
canal
Greater and
lesser palatine
canals
Petrotympanic
fissure
Facial nerve
Chorda tympani N.
Stylomastoid
Foramen
Infratemporal
fossa
Facial nerve
The third branch of the facial nerve, the chorda tympani nerve, branches from the
descending portion of the facial nerve and enters the middle ear. Within the middle ear
the chorda tympani nerve crosses the medial surface of the tympanic membrane. It then
passes through the petrotympanic fissure to enter the infratemporal fossa.
Click here to start Animation
Overview of Facial
Nerve anatomy in
the skull
Hiatus of canal of greater
superficial petrosal nerve
Internal
Acoustic
Meatus
Posterior
Cranial
Fossa
Inferior Orbital Fissure
Lacerate foramen
Pterygoid
canal
Greater
superficial
Petrosal
nerve
(GSPN)
Facial
canal
Petrotympanic
fissure
Facial nerve
Stylomastoid
Foramen
Facial nerve
Posterior
auricular N.
Chorda tympani
Parotid
region
The descending portion of the facial nerve exits the facial canal at the
stylomastoid foramen and continues into the parotid region
Click here to start Animation
Greater and
lesser palatine
canals
Functional components of the
Facial Nerve (CN VII)
1.
2.
3.
4.
5.
• SVE (Special Visceral Efferent) — Motor to
striated muscles derived from the 2nd branchial
arch.
• GVA (General Visceral Afferent) — Sensory
from visceral touch, temperature, and pain.
• SVA (Special Visceral Afferent) — Taste
• GVE (General Visceral Efferent) — Autonomic
innervation to mucosal, lacrimal, and salivary
glands.
• GSA (General Somatic Afferent) — Sensory
from somatic touch, temperature, and pain.
Click on numbers for functional components
SVE Component of the
Facial Nerve
1.
2.
3.
4.
5.
The next 11 slides demonstrate innervation to
muscles derived from the 2nd branchial arch:
Stapedius muscle -- dampens movement of the
ossicles (inserts on stapes of middle ear)
Posterior auricular muscle -- posterior movement
of pinna
Stylohyoid muscle -- elevates hyoid bone
Posterior belly of digastric -- elevates hyoid
bone, depresses mandible
Muscles of facial expression -- blinking, smiling,
frowning, facial movements
Click here to start Animation of SVE component
1. The Stapedius muscle dampens movement of the ossicles
SVE
\
Stapedius muscle dampens movement of the
ossicles protecting the inner ear from
damage from loud noises
Click here to start Animation
2. The Posterior Auricular nerve innervates the posterior
auricular muscle, pulling the pinna posteriorly.
SVE
Posterior auricular
muscle pulls the
pinna posteriorly
SVE
component of
posterior
auricular nerve
Click here to start Animation
3. The Stylohyoid muscle elevates the hyoid bone
SVE
Through the internal
Acoustic meatus
Stylohyoid
muscle elevates
the hyoid bone.
Through the
stylomastoid
foramen
Stylohyoid branch of
facial nerve
innervates stylohyoid
muscle
Click here to start Animation
4. The Posterior belly of digastric muscle elevates the hyoid bone
SVE
Through the internal
acoustic meatus
Posterior belly of
digastric muscle
elevates the
hyoid bone
Through the
stylomastoid
foramen
Posterior belly of
digastric branch of
facial nerve
innervates posterior
belly of digastric
muscle.
Click here to start Animation
5. The next six slides demonstrate SVE innervation to
the muscles of facial expression*
A.
Temporal branch (with zygomatic
branch) innervates orbicularis oculi-closes eyelids
B.
Zygomatic branch (with buccal branch)
innervates zygomaticus major--smiling
C.
Buccal branch innervates
buccinator--tenses cheek
D.
Mandibular branch innervates
depressor angularis oris--frowning
E.
Cervical branch innervates platysma -lowers mandible, tenses skin of anterior
neck
SVE
*These are key innervations to the muscles
of facial expression. However, each nerve
branch innervates multiple muscles and
each muscle receives multiple nerve
branches.
A. The temporal and zygomatic branches of the facial
nerve provide SVE nerve fibers that innervate the ipsilateral
orbicularis oculi, the muscle responsible for closing the
eyelid.
Contraction of orbicularis
oculi causes the eyelid to close
SVE
Temporal branch
Zygomatic branch
Click here to start Animation
B. The zygomatic and buccal branches of the facial nerve
innervate the ipsilateral zygomaticus major muscle, the
main muscle responsible for smiling.
SVE
Zygomaticus
major muscle
Zygomatic branch
Contraction of the zygomaticus major muscle
causes smiling
Click here to start Animation
C. The buccal branch of the facial nerve innervates the
buccinator muscle, the muscle responsible for holding the
cheek against the teeth, thus positioning food for chewing.
SVE
Contraction of the buccinator muscle
causes tensing of the cheek which
helps position food within the occusal plane
for chewing
Buccal branch of
facial nerve innervates
Buccinator muscle.
Click here to start Animation
D. The mandibular and buccal branches of the facial nerve
innervate the ipsilateral depressor angularis oris muscle, a
muscle responsible for frowning.
SVE
Mandibular
branch
Depressor
angularis oris
Click here to start Animation
Contraction of the
depressor angularis oris
muscle causes frowning
E. The cervical branch of the facial nerve innervates the
platysma muscle, a muscle partly responsible for depressing the
mandible.
SVE
Contraction of platysma
Muscle results in depression
of mandible.
Platysma muscle
Cervical branch of
facial nerve innervates
Platysma muscle.
Click here to start Animation
E. The cervical branch of the facial nerve innervates the
platysma muscle (the “shaving muscle”), a muscle
responsible for tightening the skin of the anterior neck.
SVE
Contraction of platysma
muscle causes the skin of the
anterior neck to tighten.
Platysma muscle
Cervical branch of
facial nerve innervates
Platysma muscle.
Click here to start Animation
Summary of
SVE
Internal Acoustic
Meatus
Facial
nucleus
Stapedius muscle
dampens
movement of
ossicles.
Facial
canal
Facial nerve
Stylomastoid
Foramen
Facial nerve
Posterior
auricular N.
Posterior auricular
muscle responsible for
posterior displacement
of pinna.
Stylohyoid muscle
elevates hyoid bone.
Posterior belly
of digastric
elevates hyoid
bone.
Click here to start Animation
Temporal-orbicularis oculi
closes eyelids.
Zygomatic-zygomaticus major
partly responsible for smiling.
Buccal-buccinator tenses cheek
Mandibular-depressor angularis
oris responsible for frowning.
Cervical- platysma helps lower
mandible and tightens skin of
neck.
GVA Component of the
Facial Nerve
The next slide demonstrates that GVA is
responsible for providing:
1. Light touch, temperature, and pain
sensation from the soft palate via the
greater superficial petrosal nerve
(GSPN).
Click here to start GVA
1. GVA provides sensation of light touch,
temperature, and pain from the soft palate.
GVA
Temperature sensation
GSPN
soft
palate
Light touch sensation
Pain sensation
Facial nerve
Light touch, temperature,
and pain from
the soft palate
Click here for animation
Through the
Pterygoid canal
Summary
of GVA
Through the
hiatus of canal of
GSPN
GSPN
Through the
internal acoustic
meatus
Facial
canal
Facial nerve
Light touch,
temperature,
and pain from
the soft palate
Click here for animation
Pterygoid
canal
Through the
lesser palatine
canal
SVA Component of the
Facial Nerve
The next two slides demonstrate that SVA
is responsible for providing:
1. Taste from the hard and soft palate via
the greater superficial petrosal nerve
(GSPN).
2. Taste from the anterior 2/3 of the
tongue via the chorda tympani nerve.
Click here for animation
1. SVA provides taste sensation from the hard and
soft palate via the GSPN.
SVA
Hard palate
Soft
palate
GSPN branches from
the facial nerve at the
geniculate ganglion
within the genu of the
facial canal. It is made up
of fibers from SVA,
GVE, and GVA.
Co
Sweetened
coffee
Taste from the hard
and soft palate
Click here for animation
2. SVA provides taste to the anterior 2/3 of
the tongue via the chorda tympani nerve.
SVA
Chorda
tympani
Taste from the anterior
2/3 of the tongue
Click here for animation
Summary
of SVA
Hiatus of canal of greater
superficial petrosal nerve
Internal
Acoustic
Meatus
Lacerate foramen
GSPN
Pterygoid
canal
Facial
canal
Petrotympanic
fissure
Chorda tympani
Taste from hard
and soft palate.
Stylomastoid
Foramen
Taste from
anterior 2/3
tongue.
Click here to start animation
Greater and
lesser palatine
canals
GVE Component of the
Facial Nerve
1. Via the pterygopalatine ganglion GVE provides:
A. Lacrimation (tearing of the eye)
B. Mucus secretions of the nasal cavity
C. Mucus secretions of the oral cavity
2. Via innervation of the submandibular ganglion
GVE provides:
A. Salivation of the oral cavity
Click to start Animation of GVE component
1. The GVE component of the facial nerve transmits preganglionic
fibers to the pterygopalatine ganglion via the GSPN. From the
pterygopalatine ganglion postganglionic fibers cause ipsilateral
lacrimation and mucus secretions of the nasal and oral cavities.
GVE
GSPN
Lacrimal gland
Pterygopalatine
ganglion
A. Tearing of eye
Lacrimal nucleus
B. Mucus secretion of
nasal cavities
C. Mucus secretion
of hard and soft
palate.
Click here to start Animation
2. The GVE component of the facial nerve transmits preganglionic
fibers to the submandibular ganglion via the chorda tympani nerve.
From the submandibular ganglion postganglionic fibers innervate the
submandibular and sublingual glands, causing salivation.
GVE
Sublingulal
gland
Submandibular
gland
Superior salivary
nucleus
Chorda
tympani
Submandibular
ganglion
Click here to start Animation
Summary
of GVE
Hiatus of canal of greater
superficial petrosal nerve
Inferior Orbital Fissure
Lacerate foramen
GSPN
Greater and
lesser palatine
canals
Pterygoid
canal
Internal
Acoustic
Meatus
From the pterygopalatine ganglion
postganglionic GVE fibers
provide lacrimation of the
eyes and mucus secretion of the
nasal cavity and oral cavity.
Facial
canal
Petrotympanic fissure
Superior salivary
and lacrimal nucleus
Chorda tympani
From the submandibular
ganglion postganglionic
GVE fibers provide
salivation in the oral cavity.
Click here to start animation
GSA Component of the
Facial Nerve
GSA is responsible for providing:
1. Touch, temperature, and pain sensation from
part of the external acoustic meatus via the
posterior auricular nerve.
Click here to start GSA
1. GSA provides touch, temperature, and pain
sensation from the external acoustic meatus.
Cotton swab
GSA
Touch, temperature,
and pain sensation
from part of the
external acoustic
meatus.
Posterior
auricular
nerve
Click here to start animation
Foramen Rotundem
Summary of
GSA
Internal Acoustic
Meatus
Facial
canal
Facial nerve
Stylomastoid
Foramen
Facial nerve
Touch, temperature,
and pain sensation
from the external
acoustic meatus.
Posterior
auricular
nerve
Click here to start animation
Inferior Orbital Fissure
Summary of functional components
• Each of the five functional components of the
facial nerve SVE, GVA, SVA, GVE, and GSA
have a unique function. Knowledge of these
functional components can be applied to clinical
observations to aid in localizing lesions of nerve
branches or at anatomical landmarks.
• The following slides provide examples of how
lesions at different locations can effect function.
Question #1
One effect of a lesion here, between
the branching of the stapedial nerve
and the branching of the chorda
tympani nerve, would be:
A. Paralysis
of facial
muscles
A. Paralysis
of facial
muscles
B. Decreased
sensationof
soft
palate
B. Decreased
sensation
soft
palate
C. Decreased
hearingto
sensivity
C. Increased
sensitivity
loud noise
D. LossD.ofLoss
taste
of hard
of taste
to thepalate
soft palate
Question #2
A lesion here, between the
branching of the stapedial nerve
and the branching of the chorda
tympani nerve, will also cause?
A. Loss of light touch from the soft palate
B. Loss of taste from the soft palate
C. Loss of taste of anterior 2/3 of tongue
D. Loss of temperature from the soft palate.
Question #3
One effect of a lesion here, at the
stylomastoid foramen will be:
A. Loss of light touch from the soft palate
B. Loss of salivation of oral cavity
C. Increased sensitivity to loud noises
D.Partial loss of sensation of external acoustic meatus
Question #4
A lesion here, between the branching
of the GSPN and the branching of the
stapedial nerve, will spare:
A. Taste of anterior 2/3 of tongue
B. Taste of hard palate
C. Salivation in oral cavity
D. Ipsilateral facial expression
Question #5
A lesion here, between the
branching of the GSPN and the
branching of the stapedial nerve,
will also spare:
A. Light touch from the soft palate
B. Ability to smile
C. Taste from the anterior 2/3 of tongue
D. Protection of the inner ear from loud noises
Thank You
Return to SVE
Return to GVA
Return to GVE
Return to SVA
Return to GSA
Return to Lesion Questions
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing sensation from the soft palate.
Please try again
Incorrect
The stapedial nerve (SVE), which is spared by this lesion, is
responsible for protecting the ear from increased sensitivity to loud
noises.
Please try again
Incorrect
The SVA component of the GSPN, which is spared by this lesion,
is responsible for providing taste from the hard palate.
Please try again
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing light touch from the soft palate.
Please try again
Incorrect
The SVA component of the GSPN, which is spared by this lesion,
is responsible for providing taste from the soft palate.
Please try again
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing temperature sensation from
the soft palate.
Please try again
Incorrect
The GVA component of the GSPN, which is spared by this lesion,
is responsible for providing light touch from the soft palate.
Please try again
Incorrect
The GVE component of the chorda tympani nerve, which is spared
by this lesion, is responsible for providing salivation
of the oral cavity.
Please try again
Incorrect
The stapedial nerve (SVE), which is spared by this lesion, is
responsible for protecting the ear from increased sensitivity to loud
noises.
Please try again
Incorrect
This lesion will not spare taste to the anterior 2/3 of the tongue,
which is supplied via the SVA component of the chorda tympani
nerve.
Please try again
Incorrect
This lesion will not spare salivation of the oral cavity, which is
supplied by the GVE component of the chorda tympani nerve.
Please try again
Incorrect
This lesion will not spare ipsilateral facial expression, which is
supplied by the temporal, zygomatic, buccal, mandibular, and
cervical branches of the facial nerve (SVE).
Please try again
Incorrect
This lesion will not spare the ability to smile, which is supplied by
the zygomatic branch of the facial nerve (SVE).
Please try again
Incorrect
This lesion will not spare the ability to taste from the anterior 2/3 of
the tongue, which is supplied by the SVA component of the chorda
tympani nerve.
Please try again
Incorrect
This lesion will not spare the ability to smile, which is supplied by
the zygomatic branch of the facial nerve (SVE).
Please try again
Incorrect
This lesion will not spare the ability to protect the ear from loud
noises, which is supplied by the stapedial nerve (SVE).
Please try again
Correct!
A lesion here will cause paralysis of facial muscles due
to its disruption of the SVE component.
Go back to question 1
Next question
Correct!
A lesion here will cause a loss of taste to the anterior 2/3 of the
tongue due to the disruption of the SVA component of
the chorda tympani nerve.
Go back to question 2
Next question
Correct!
A lesion here will cause partial loss of sensation (light touch,
temperature, and pain) of the external acoustic meatus due to
disruption of the GSA component of the posterior auricular nerve.
Go back to question 3
Next question
Correct!
A lesion here will spare a person’s ability to taste on the hard and soft
palate because the SVA component of the Greater Superficial Petrosal
Nerve (GSPN) remains intact.
Go back to question 4
Next question
Correct!
A lesion here will spare the sensation of light touch of the soft palate
because the GVA component of the GSPN remains intact.
Go back to question 5
Continue