CN V: Trigeminal Nerve
➢ Largest cranial nerve
- Sensory nerve – To greater parts of the head
- Motor nerve – to several muscles including muscles of
mastication
- Divided into three branches:
o Ophthalmic Nerve (V1) – Sensory
o Maxillary Nerve (V2) – Sensory
o Mandibular Nerve (V3) – Mixed Motor and
Sensory (Nuclei of these branches originated
from the brainstem)
1. Mesencephalic Nucleus
➢ Composed of a column of Unipolar Nerve Cells in the lateral part
of the gray matter and around the cerebral aqueduct and extends
inferiorly to the pons as far as the main sensory nucleus
➢ Proprioception of your temporomandibular joint TMJ, and
muscles of mastication, periodontal ligament (during mastication,
you should know what body part is in control: chief sensory
nucleus will sense pressure and touch of your face and your spinal
nucleus will sense the temperature and pain sensation of your
face > 3 divisions supply the sensation to your face).
**Note: Trigeminal neuralgia - a chronic pain condition that affects the trigeminal nerve,
which carries sensation from your face to your brain. If you have trigeminal neuralgia,
even mild stimulation of your face — such as from brushing your teeth or putting on
makeup — may trigger a jolt of excruciating pain**
Chief Sensory Nucleus
➢ Main sensory nucleus
➢ Posterior part of the pons, lateral to the motor nucleus, and
continuous below with spinal nucleus
➢ Senses of Pressure and Touch in the face
Spinal Nucleus
➢ Continuous superiorly with the main sensory nucleus in the pons
➢ Extends inferiorly through the whole length of the medulla
oblongata and into the upper part of the spinal cord as far as the
second cervical segment
➢ Temperature and Pain sensation in the face
➢ Sensory fibers of the Spinal Nucleus
- Ophthalmic Division - Terminate in the inferior part of
the spinal nucleus.
- Maxillary Division - Terminate in the middle of the
spinal nucleus.
- Mandibular Division - End in the superior of the spinal
nucleus
Trigeminal Ganglion
➢ Sensory fibers in the trigeminal nerve have their cell bodies in the
trigeminal ganglion.
➢ Crescent-shaped
➢ Lies within a pouch of the dura mater – Trigeminal or Meckel Cave
➢ Ophthalmic, maxillary, and mandibular nerves arise from the
anterior border of the ganglion
- N. Ophthalmicus Ophthalmic Nerve (V1)
- Maxillary nerve (V2)
- Mandibular nerve (V3)
Trigeminal Nerve and Motor Nucleus: Muscles of Mastication and Tensor
Tympani Membrane
➢ Motor Nucleus
- Has no ganglia
- Receives:
✓ Corticonuclear Fibers from both
hemispheres
✓ Fibers from the Reticular Formation, the
Red Nucleus, Tectum, and Medial
Longitudinal Fasciculus
✓ Fibers from the Mesencephalic Nucleus
forming a Monosynaptic Reflex Arc
- Cells give rise to axons forming the motor root.
- Supplies the muscles of mastication, (if you are
chewing on something, remember your CN V)
➢ Tenses your tympanic membrane (eardrum), Tensor Tympani,
Tensor Veli Palatine, and Mylohyoid and the anterior belly of the
digastric muscle
CN V1: Ophthalmic Nerve (Sensory)
➢ Contains only sensory fibers
➢ Exits through the Superior Orbital Fissure and enters the Orbital
Cavity
1. Lacrimal Nerve
- A sensory to Tear Duct, Sclera of Eye, Cornea, Lateral
part of Upper Eyelid
2. Frontal Nerve
- Supra-Orbital nerve: sensation of Forehead
- Supra-Trochlear nerve: Bridge of nose, Medial side of
Forehead
- Branch to frontal and Ethmoid Sinus
3. Nasocillary Nerve
- Sensation of Nasal Cavity, Sphenoid Sinus, Superficial
part of nose, Meningeal branch (Tentorium Cerebelli)
CN V2: Maxillary Nerve (Sensory)
➢ Contains only Sensory Nerve Fibers
➢ Exits through the Foramen Rotundum
1. Greater and Lesser Palatine nerve
- Nasopharynx
- Posterior part of nasal cavity
Hard and soft palate
2. Superior alveolar nerve
- Upper teeth
3. Infra-orbital nerve
- Upper Lip, Upper Jaw, Nostrils
4. Zygomatic nerve
- Zygomatico-Temporal nerve
✓ Lateral side of Forehead
- Zygomatico-Facial nerve
✓ Skin of cheekbone
Anterior Division (supply the muscles of mastication)
➢ Medial Pterygoid nerve
- Tensor Tympani (tenses eardrum)
- Tensor Veli Palatine (tenses palate)
➢ Masseter nerve
- Masseter muscle
➢ Deep temporal nerve
- Temporal muscle
➢ Lateral Pterygoid nerve
- Lateral Pterygoid muscle
➢ Buccal nerve
- Mucosa Oral Cavity
2. Posterior Division
➢ Auriculo-Temporal nerve
- Side of the head
- Sensory external acoustic meatus
- Proprioception TMG
➢ Inferior Alveolar nerve
- Teeth of the lower jaw
- Gums
- Skin of the Lower Jaw
➢ Mental nerve
- Skin Lower Lip
➢ Lingual nerve
- Parasympathetic and Touch fibers from Chorda
Tympani
- General sensory to the anterior 2/3 of the tongue
**Note: Taste is secondary to your facial nerves. Mandibular has a sensory root (only one
that has a ganglion) and a motor root (directly attached to the mandibular nerve)**
• Somato-Motor Functions
➢ Muscles of mastication:
✓ Temporalis muscle
✓ Masseter, Medial, and Lateral Pterygoid muscles
➢ Suprahyoidal muscles:
✓ Mylohyoid
✓ Anterior belly of the Digastric muscle
**Note: There are two nerves supplying suprahyoid muscle: mandibular nerve and
facial nerve. Contraction of the suprahyoid muscles will pull up the hyoid bone, allowing
you to swallow**
✓ Mylohyoid and anterior belly of the digastric muscle
➢ Tensor tympani:
✓ Tensor to the eardrum - Found in the inner ear
protection against loud noises
➢ Tensor villi Palatini:
✓ Tensor to the palate
Mandibular Nerve: Motor to Muscles of Mastication
➢ Masseter (superficial and deep head)
➢ Temporalis
➢ Medial Pterygoid
➢ Lateral Pterygoid
1. All supplied by the CN V3
2. All originated in the skull and attached to mandible
3. Paired
**Note: How to test the somato-motor? Just tell the patient to open and close his mouth
and move his mouth from side to side. How to examine somatosensory? Anything that
is painful to the face comes from your mandibular nerve**
• CN V: Somato-Sensory
➢ Sclera/Cornea of the eye
➢ Anterior 2/3 of the tongue
➢ Mucosa of nasal cavity, sinuses, and oral cavity
➢ Teeth
➢ Part of external side of eardrum
➢ The meninges in the anterior and middle cranial fossa
➢ All meninges superior to tentorium cerebelli
➢ Proprioceptive action of:
- Temporomandibular joint
- Muscles of mastication
- Periodontal ligaments
Brainstem
1. Motoric nucleus (somato-motor)
➢ Location
- Deep in reticular formation of lower part of the pons.
➢ Voluntary Control
- The part of the nucleus that supplies the muscles of the
lower part of the face receives only corticonuclear
fibers from the opposite cerebral hemisphere.
➢ Involuntary Control
- Separate and controls mimetic or emotional changes in
facial expression. This other other pathway forms part of the
reticular formation.
Superior salivary nucleus (Parasympathetic) – Supplies the
Submandibular and Sublingual Glands
➢ Location:
- Parasympathetic nuclei lie posterolateral to the main
Motor nucleus
➢ Superior salivatory
- Receives afferent fibers from the Hypothalamus
through the Descending autonomic pathways.
Information concerning taste also is received from the
nucleus of the solitary tract from the mouth cavity.
➢ Lacrimal nucleus
- Receives afferent fibers from the hypothalamus for
emotional responses and from the sensory nuclei of
the trigeminal nerve for reflex lacrimation secondary
to irritation of the cornea or conjunctiva.
Step 1: It enters the Cerebellopontine angle and the internal auditory meatus,
together with the Vestibulocochlear nerve
**Note:
Fracture to the skull that damages the internal auditory meatus will cause
paralysis to the face**
• Step 2: It will then innervate to Stapedius muscle (responsible for reducing
loud sound -smallest muscle of the body)
• Question: What is the blood supply of your stapedius muscle? A: Facial nerve.
Q: What is its bone? A: Stapes (smallest bone)
• Step 3: It enters the facial canal, then goes to the parasympathetic branch of
the submandibular and sublingual gland (Supplied by your facial nerve)
• Step 4: It enters under the parotid gland and now supply the muscles of facial
expressions.
Canalis facialis - Geniculate ganglion
• Greater petrosal nerve > Sphenopalatine ganglion
➢ Lacrimal gland
➢ Mucosa nose, sinuses, upper mouth, Eustachian tube, middle ear
• Chorda tympanic nerve > Submandibular ganglion
➢ Parasympathetic for submandibular and sublingual glands
➢ Taste fibers 2/3 of tongue
• Stylomastoid foramen
➢ Stylohyoidues muscle + Posterior belly of digastric muscle
➢ Posterior auricular nerve
- Rudimentary posterior ear muscles
- Posterior belly Occipitofrontal muscle.
- Small part of skin posterior from ear, part of the ear,
part of the external side of ear drum and external
acoustic meatus
Parotid gland
➢ Supplied by the glossopharyngeal nerve
- Temporo-facial division
✓ Temporal r. – temporal m. + upper part of
orbicular m.
✓ Zygomatic r. – lower part of orbicular m.,
muscles of nose
✓ Buccalis r. - buccinator m. and orbicularis oris m.
- Cervico facial division
✓ Buccalis r.
✓ Mandibular r. – Mental m. + lower part of
orbicularis oris m.
✓ Cervical r. – platysma m.
Branches of the Facial Nerve
• Temporalis branches
• Zygomatic branches
• Buccal branches
• Mandibular branch
• Cervical branch
• Posterior Auricular Branch
II. Somato-Motor
• Muscles of facial expression
• AKA: Emojis
• Stapedius Muscle
• 2 Suprahyoid muscles:
- Stylohyoid
- Posterior belly of the digastric muscle
- Nerve to stapedius (Facial Nerve)
- Dampens vibration of the Stapes (Control the
amplitude of sound waves from external environment
to inner ear)
- Paralysis (damage to CN VII): Increase oscillation of
the stapes
✓ “Hyperacusis”
✓ Normal sounds perceived as very loud
**Note: Smallest bone in the body: Stapes; Smallest muscle in the body: Stapedius
muscle**
Somato-sensory
• Outer part of the tympanic sheet
• Part of outer ear (external auditory meatus)
• Part of posterior ear (pinna)
IV. Visceromotor (Parasympathetic)
• Parasympathetic visceromotor
➢ Tear (Lacrimal) gland
➢ Submandibular, Sublingual salivary glands (saliva)
➢ Mucosa of the nose cavity, sinuses, part of buccal
cavity, Eustachian tube and the middle ear
➢ Lacrimal Gland (Tear)
➢ Sensory (Afferent): Ophthalmic nerve (CN V1)
➢ Visceromotor (Efferent): Greater petrosal nerve (CN
VII)
V. Special Sense
Course of the Facial Nerve
- Roots emerges from the anterior surface of the brain
between the pons and the medulla oblongata
- Both laterally passes the Posterior Cranial Fossa with
the Vestibulocochlear nerve and enter the Internal
Acoustic Meatus in the petrous part of the Temporal
bone
- In the bottom of the Meatus, It enters the Facial canal
and runs laterally through the inner ear. Reaching the
medial wall of the Tympanic cavity, the nerve expands
to form the Sensory Geniculate Ganglion.
- It sharply turns backward above the Promontory. At
the posterior wall of the tympanic cavity, the facial
nerve turns downward on the medial side of the Aditus
of the Mastoid Antrum, descends behind the pyramid,
and emerges from the Stylomastoid foramen.
❖ Motor Root
- Travel posteriorly around the medial side of the
Abducent nucleus then pass around the nucleus
beneath the Colliculus Facialis in the floor of the fourth
ventricle and finally pass anteriorly to emerge from the
brainstem.
❖ Sensory Root
- Formed from the central processes of the Unipolar
cells of the Geniculate ganglion. It also contains the
efferent Preganglionic Parasympathetic fibers from the
Parasympathetic nuclei.
Distribution of the Facial Nerve
1. Motor nucleus
- Supplies the muscles of facial expression (Auricular
muscles, Stapedius, Posterior Belly of the Digastric, and
Stylohyoid Muscles)
2. Superior Salivatory Nucleus
- Supplies
➢ Submandibular and Sublingual salivary glands
➢ Nasal and Palatine glands
3. Lacrimal nucleus
- Supplies the Lacrimal gland.
4. Sensory nucleus
- Receives taste fibers from the anterior two- thirds of
the tongue, the floor of the mouth, and the palate.
REMEMBER:
CN VII Functions:
o “Face, Ear, Taste, Tear, Saliva”
o Face: Muscles of Facial expression and Blinking
o Ear: motor to Stapedius muscle (Dampen loud noises) and sensory to EAM
and Pinna
o Taste: Anterior 2/3 of tongue
o Tear: Parasympathetic (Visceromotor) supply to Lacrimal glands
o Saliva: Parasympathetic (Visceromotor) supply to Salivary glands
(Submandibular/Sublingual glands)
**Note: There is a bilateral or dual contribution of the primary motor cortex to the
forehead**
FACIAL NERVE EXAMINATION
o Crease up the forehead
o Reveal the teeth
o Keep eyes closed against resistance
- Oculomotor nerve: open the eyes against resistance
- Facial nerve: eyes closed against resistance
o Puff out the cheeks
Central (UMN) vs Peripheral (LMN) Facial Paralysis/Paresis
➢ Upper motor neuron (UMN)
- Central Facial weakness/paralysis
- Paralysis/weakness of muscles of
the contralateral lower face
- Bilaterally preserved forehead
▪ The forehead will be intact but there will be
a shallow naso-labial fold contralateral to
the lesion so the lesion here is in the right
motor cortex
- Example: Stroke affecting left motor cortex or any
portions of the tract (Internal capsule on the left side)
➢ Lower motor neuron
- Peripheral facial paralysis/weakness
- All muscles are affected (forehead and lower face)
ipsilateral to the lesion
- Example: Bell’s Palsy lesion/damage on left CN VII
▪ If you cut the facial nerve here all that side
will be paralyzed ipsilateral to the lesion
▪ Q: What is the affected nerve in mumps
parotitis? A: Facial Nerve VII – Bell’s Palsy
Corneal Reflex: Blink Reflex
• Involuntary blinking of eyelids on stimulation of the cornea
(Corneal reflex) or a sudden exposure to a very bright light (Optical
reflex)
• Very rapid: 0.1 secs
• Direct and consensual response (opposite eye)
- That means that the opposite eye will always blink. Not
unless the foreign body lodges in the sclera. Because
the sclera is not involved in the blink reflex
• Means to protect eye from foreign bodies/bright lights
• Also occurs with sounds > 40-60 db (sudden and not anticipated)
- The blink reflex is also a reaction to sound
• Mediated by
- Afferent: Nasociliary branch of Opthalmic nerve (V1) –
supply sensation to the cornea
- Efferent: Temporal and zygomatic branches of Facial
Nerve (VII) thru Orbicularis Oculi Muscle (closes the
eye, the muscle surrounding the eye)
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