The trigeminal nerve Flashcards
The trigeminal is the … cranial nerve
Vth or 5th
Describe the trigeminal nerve. Which fibres does it contain?
The trigeminal nerve is the largest cranial nerve and contains both sensory and motor fibers
The trigeminal nerve receives 3 large sensory nerve, namely :
▪ upper(ophthalmic n.)
▪ middle (maxillary n.)
▪ lower (mandibular n.) (+motor)
Name the 4 nuclei of the trigeminal nerve.
- Main sensory nucleus
- Spinal nucleus
- Mesencephalic nucleus
- Motor nucleus
Where does the main sensory nucleus lie?
In the posterior part of pons lateral
to the motor nucleus
What is the spinal nucleus continuous with superiorly?
The spinal nucleus is continuous superiorly with main sensory nucleus and extends inferiorly through medulla oblongata and into upper part of spinal cord as far as second cervical segment
What is the mesencephalic nucleus composed of?
The mesencephalic nucleus is composed of unipolar cells situated in lateral part of gray matter around cerebral aqueduct and it extends inferiorly into pons as far as the main sensory nucleus
Where is the motor nucleus situated?
In the pons medial to the main sensory nucleus
The course of the trigeminal nerve(from the pons) :
❑Trigeminal nerve leaves
anterior aspect of pons as a
small motor root and a large
sensory root
❑Each root is ensheathed in
pia-arachnoid
❑It passes forward out of posterior cranial fossa and rests on apex of petrous bone in middle cranial fossa here sensory root expands to form trigeminal ganglion
❑Ophthalmic, maxillary, and
mandibular nerves arise from
the anterior border of ganglion
Course of the trigeminal nerve(from the skull) :
❑Ophthalmic nerve (V1) contains only sensory fibers leaves skull through superior orbital fissure to orbital cavity ❑Maxillary nerve (V2) also contains only sensory fibers leaves the skull through foramen rotundum ❑Mandibular nerve (V3) contains both sensory and motor fibers and leaves skull through foramen ovale ❑The sensory fibers to skin of face from each division supply a distinct zone with little or no overlap of dermatomes
What type of ganglion is the trigeminal ganglion?
A sensory ganglion
What is the trigeminal ganglion made up of?
The trigeminal ganglion is made up of pseudounipolar nerve cells, with a “T-shape” arrangement of
processes arising from the cell bodies, which divide to form the central and
peripheral processes
Where does the trigeminal ganglion lie?
Lies in the trigeminal impression on the anterior surface of the petrous temporal
bone near the apex
What does the trigeminal ganglion occupy?
It occupies a special space of dura called the Meckel’s cave or the Trigeminal cave
The relations of the trigeminal ganglion :
▪Medially – ICA and posterior part of cavernous sinus ▪Laterally – Middle meningeal artery ▪Superiorly – Parahippocampal gyrus ▪Inferiorly – Motor root of Vth CN; greater petrosal nerve; apex of petrous bone; foramen lacerum
SENSORY COMPONENT OF TRIGEMINAL NERVE : What are the branches of the unipolar cells of the trigeminal ganglion divided into?
Branches of the unipolar cells of the trigeminal ganglion are divided into central
and peripheral branches
Describe the peripheral processes of the unipolar cells.
The peripheral processes of the unipolar cells are sensory
What do the central processes of the unipolar cells form?
The central processes of the unipolar cells
form sensory root of trigeminal nerve
About half the fibers divide into…
ascending
and descending branches
when they enter the pons
Where do the ascending branches terminate?
Ascending branches terminate in
main sensory nucleus
Where do the descending branches terminate?
Descending branches terminate in
spinal nucleus
Where do the touch and pressure nerve fibers terminate?
Touch and pressure nerve fibers
terminate in the main sensory nucleus
Where does pain and temperature pass?
Pain and temperature pass to spinal
nucleus
The remaining fibers ascend or descend in the…
brainstem without division
What are the proprioceptive impulses from the muscles of mastication carried by?
Proprioceptive impulses from muscles of mastication are carried by fibers of unipolar cells of the mesencephalic nucleus that have bypassed the trigeminal ganglion
What happens to the axons in the main sensory nuclei and central processes of cells in the mesencephalic nucleus?
Axons in the main sensory nuclei, spinal nuclei and central processes of cells in mesencephalic nucleus crosses the median plane and ascend as the trigeminal lemniscus is going to terminate on nerve cells of ventral postero-medial nucleus of the thalamus.
What do the axons travel through?
Axons travel through genu internal
capsule to postcentral gyrus
MOTOR COMPONENT OF TRIGEMINAL NERVE : Where does the motor nucleus lie?
Motor nucleus lies in grey
matter beneath rhomboid
fossa
MOTOR COMPONENT OF TRIGEMINAL NERVE : What do the cells of the motor nucleus give rise to?
Cells of motor nucleus give
rise to axons that form motor
root
MOTOR COMPONENT OF TRIGEMINAL NERVE : What does the motor nucleus supply?
Motor nucleus lies in grey matter beneath ❑Motor nucleus supplies muscles of mastication, tensor tympani, tensor veli palatini, mylohyoid and anterior belly of digastric muscle.
Describe the ophthalmic nerve[Va]
- The ophthalmic nerve[Va] is the smallest of 3 peripheral branches of trigeminal
- The ophthalmic nerve is a sensory nerve
The cutaneous branches supplies structures derived from frontonasal
prominence i.e.
- Eyeball
- Lacrimal gland
- Conjunctiva
- Nasal & paranasal mucosa
- Skin of scalp, forehead, eyelids and nose
Course of the ophthalmic nerve(Va) :
❑ Passes forwards from trigeminal cave
❑ Through the lateral wall of cavernous sinus:
▪ above maxillary n.
▪ below trochlear n.
❑ Divides into three branches (Frontal; Lacrimal and Nasociliary nerves) prior to
entry into superior orbital fissure to enter into the orbit
BRANCHES OF OPHTHALMIC NERVE (Va) : Frontal nerve. Describe the frontal nerve.
The frontal nerve is the largest of 3 terminal branches of Va
BRANCHES OF OPHTHALMIC NERVE (Va) : The frontal nerve passes…
forwards in orbit just under its roof and ½ way through it divides into the:
- Supratrochlear nerve
- Supraorbital nerve
Describe the supratrochlear nerve.
The supratrochlear is the smallest terminal branch
Where and how does the supratrochlear nerve run?
The supratrochlear nerve runs anteromediallly in the roof of the orbit, passing above trochlear nerve
and emerges through the frontal notch
Which structures does the supratrochlear nerve supply?
The conjunctiva; skin of upper eyelid and skin of midline of forehead
above root of nose
Describe the supraorbital nerve.
The supraorbital nerve is a larger terminal branch
What does the supraorbital nerve transverse?
The supraorbital nerve transverses through the supra-orbital foramen
What does the supraorbital nerve supply?
The scalp up to vertex, rest of
forehead, central upper eyelid;
conjunctiva and frontal sinus
BRANCHES OF OPHTHALMIC NERVE (Va) : The lacrimal nerve. Describe the lacrimal nerve.
The lacrimal nerve is the smallest of the 3 terminal branches of Va
BRANCHES OF OPHTHALMIC NERVE (Va) : Where does the lacrimal nerve enter the orbit?
The lacrimal nerve enters the orbit through the lateral part of the superior orbital fissure
BRANCHES OF OPHTHALMIC NERVE (Va) : The lacrimal nerve receives communication from the…
zygomatico-temporal nerve and passes deep to
the lacrimal gland
BRANCHES OF OPHTHALMIC NERVE (Va) : Which structures does the lacrimal nerve supply?
▪ Conjuctiva and upper eyelid laterally
▪Parasympathetic and sensory to lacrimal gland
And the lacrimal nerve sends Secretomotor fibres to the gland
from the greater petrosal nerve
via the zygomatico-temporal
nerve