والجاللة العزة رب الله بسمTrigeminal Nerve

Trigeminal nerve is the largest cranial nerve. It’s cranial nerve number V (it’s the largest cranial nerve). It originates from the lateral aspect of the pons in the brain with two roots: a large sensory root "its an afferent mean also راجعات composed of the process of neuron" and a small motor root "its an efferent".

*where does those neuron located?

- in the trigeminal ganglion.

*what is the smallest cranial nerve?

-it’s the trochlear the most slender one.

The large sensory root is composed of processes of neuron cells of the trigeminal ganglion.

The small motor root usually descends out through foramen ovale as part of the mandibular nerve (3rd branch of the trigeminal). Motor function is only carried by the mandibular branch of the trigeminal nerve.

*What is a ganglion?

A ganglion is the aggregation of nerve cell bodies that synapse with each other in the peripheral nervous system .

*What is the trigeminal ganglion?

Trigeminal ganglion is sensory so it is made up of synaptic sensory axons, after the synapse the sensory neurons clear into a sensory root into the brain.

Location: in the middle cranial fossa near apex of the petrous part of temporal bone

Trigeminal ganglion is ONLY sensory synapses and it only happens ONLY to sensory neurons.

Shape: It is crescent (curved) in shape; that is why sometimes it is called semi-lunar ganglion. It has a concave posterior part and convex anterior border; the convex anterior border usually produces the sensory axons forming: V1 “Ophthalmic”, V2 “Maxillary”, V3 “Mandibular”.

While the motor root passes medially and deep to the trigeminal ganglion (without entering the ganglion) through foramen ovale to become part of the mandibular nerve.

*Divisions of the Trigeminal Nerve:

Ophthalmic (V1): totally sensory nerve; usually goes to the orbit through the superior orbital fissure

Maxillary (V2): also totally sensory and passes through foramen rotundum to the pterygo-palatine fossa enter with inferior orbital fusser to floor of the orbit then infraorbital groov of the maxilla to infraorbital canal "we called it that because pass within the maxilla".

Mandibular (V3): carries both sensory and motor innervations, passing down through foramen ovale to the infratemporal notch where it divide to its all terminal branch "its very important to us as dentist".

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Starting with the ophthalmic nerve (V1):

Entirely sensory branch, sensory to the structures within the orbit (general sensation to the orbit; while special sensation to the orbit comes from the optic nerve “C.N 2”) and anterior half of the scalp (through supra-orbital and supra-trochlear branches). It is also sensory to the upper eyelid (through infra-trochlear and lacrimal nerve). And it also supplies the anterior part of the nasal cavity down to the tip of the nose (through the anterior ethmoidal nerve which gives internal and external nasal).

It divides within the middle cranial fossa just before it gets into the superior orbital fissure into three main branches, those three branches will enter the orbit through the superior orbital fissure. The branches are:

1. The frontal branch "the largest one" it divide to supra orbital & supra trochlear nerve" its gives sensation to forehead area. goes superiorly towards the frontal bone .

2.The lacrimal nerve goes laterally to the lacrimal gland "it’s the smallest one & does not go to the lacrimal gland its go to the lateral aspect of upper eyelid" its sensory" it not related to the special sensation".

3.The nasociliary : "intermediate in size & considered the 1st branch from the ophthalmic nerve " it gives five branches two the nose anterior & posterior ethmoidal two goes to eyeball short or commutating & long at last the terminal branch goes to the infra trochlear nerve" turns from the lateral to the medial aspect (“naso” referring to the nasal cavity, “ciliary” referring to the eyeball). It gives cilliary branches or nerves to the eyeball and nasal branches which are the ethmoidal branch.

Frontal nerve:

When we look at the frontal nerve we know it enters the orbit through the upper part of the superior orbital fissure, and then it passes forward on the superior aspect of the levator palpebrea superioris muscle "that levator upper eyelid", then it divides into two branches: the supra-trochlear which is the smaller one; and the supra-orbital which is the larger one.

*Frontal Nerve Branches "both of them gives sensation to the forehead":

Supra-trochlear: passes above the trochlea or superior to the superior oblique, to the medial part of the trochlea "it’s a loop a fibrous حلقه tissue contain inside it the superior oblique tendon .

Supraorbital: passes through supra-orbital foramen or notch to supply the forehead and anterior half of the scalp, it also sends a branch to the (I couldn’t hear the word) membrane covering the frontal air sinus.

Lacrimal:

A slender nerve that enters the orbit through the upper part of the superior orbital fissure, once it is in the orbit it passes on the upper border of the lateral rectus muscle and it goes into the lacrimal gland but don’t supply it "it a sensory nerve ", it goes out to supply the skin of lateral part of the upper eyelid, the autonomic parasympathetic supply to the lacrimal gland came from the facial nerve then to the pterygo-palatine ganglion ,as it passes its terminal part joins other nerve fibers, those fibers are parasympathetic secreto-motor nerve fibers to the lacrimal gland which stimulate the production of the Tears,& usually when it pass from the maxillary nerve to the lacrimal nerve to supply the lacrimal gland. (post-ganglionic parasympathetic fibers).

*Note: Greater petrosal is the pregangilionic nerve for this ganglion

It go out from petrus part of temporal bone & goes within the pterygo-palatine fossa then do a synapse in the pterygo-palatine ganglion then the post-synaptic fibers it goes out with oraclo-

tempral go out from the maxillary zygomatico-facial branch then to the lacrimal for the ophthalmic why cause its weak nerve continue

with it until they arrive to the lacrimal gland .

Nasocilliary:

It enters the orbit through the lower part of the superior orbital fissure, when it first enters it is on the lateral side, then it goes from the lateral to the medial aspect along with the ophthalmic artery over the optic nerve. After that it passes forward above the upper border of medial rectus muscle and terminates in what we call the infra-trochlear nerve.

It usually gives out FIVE branches (you have to know these branches):

1. Ciliary ganglion : it is a communicating branch to the ciliary ganglion within the orbit. The synapse between the parasympathetic fibers which go to the sphinictor pupili muscles happen here. The communicating branch just holds up the ganglion (it doesn’t have to do anything with it), it is only a sensory nerve to the eyeball (general sensation).

2. Long ciliary nerves : they enter the orbit and usually pass between the choroid and the sclera all the way anteriorly to reach the dilator pupilli muscles, those are actually sympathetic fibers, this is what happens when you go into a dark room.

3. Posterior ethmoidal nerve : passes through the posterior ethmoidal foramen in the orbit, to get into the sphenoidal air sinus and the ethmoidal air cells, mainly the posterior ethmoidal air cells, so it provides sensory innervation to the sphenoidal sinus and ethmoidal air cells "don’t arrives to the nasal cavity",(the artery arrives the nasal cavity but nerve don’t ) (important).

4. Anterior ethmoidal : gets through the anterior ethmoidal foramen, after it passes there it goes to the anterior cranial fossa, then it goes back to the roof of the nasal cavity anteriorly where it provides sensation to the anterior part of the nasal cavity; by becoming the internal and external nasal nerves, the external nasal goes outside "on bridge of the nose" to the face specifically to the external nose.

So the anterior ethmoidal nerve passes through the anterior ethmoidal foramen, enters the anterior cranial fossa, then goes through a small flex between the cribriform plate and the crista galea where there is a small opening through which it enters to get to the nasal cavity, providing the anterior nasal cavity and terminating as the external nasal nerve.

5. Infra-trochlear nerve : "the terminal branch of nasocilliary nerve" from its name (infra-trochlear) it goes below the poly "حلقه" of the superior oblique muscle to supply the skin on the medial part of the upper eyelid and even adjacent part of the nose.

The Dr. Repeats the previous notes many times while showing the movement of the nerves on the slides).

This is the story of the ophthalmic nerve.

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Maxillary nerve(V2):

Maxillary nerve is also totally sensory to the skin over the maxillary region, to the upper teeth and to the palate (General sensory).

It passes through foramen rotundum to the pterygo-palatine fossa then through the inferior orbital fusser in to the maxilla ; once it is there it starts to divide.

*what is the terminal branch for the maxillary artery ?

Spheno-palatine artery.

*Maxillary Nerve Branches:

i. Whether it is direct or indirect branches; it usually gives three dental branches:

1. Superior anterior alveolar nerve.

2. Superior middle alveolar nerve.

3. Superior posterior alveolar nerve.

(we most know each one of them what they supply ).

ii. It also gives three facial branches:

1. Infra-orbital nerve "it’s the terminal branch of maxillary nerve".

2. Zygomatico-facial nerve.

3. Zygomatico-temporal nerve.

iii. And three branches to the palate:

1. Greater palatine nerve: to the hard palate.

2. Lesser palatine nerve: to the soft palate.

3. Incisive or Naso-palatine nerve: to the anterior teeth.

iv. Also, it gives three other main branches:

1. Meningeal branch: into the middle cranial fossa.

2. Posterior lateral nasal branches: to the lateral wall of the nasal cavity (posterior half).

3. Branches to the pterygo-palatine ganglion: two communicating branches just to hold the ganglion; they have nothing to do with the ganglion.

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Starting with the first three:

I. Superior Alveolar Nerves:

1. Posterior alveolar: it is a direct branch from the maxillary nerve. It goes to provide innervations to the posterior teeth, except the mesial root of the first molar (although sometimes it does; but more often it doesn’t).

After giving that branch; the maxillary nerve enters the inferior orbital fissure to the infra-orbital groove. At the level of the inferior orbital fissure it is called the infra-orbital nerve; it passes on the floor of the orbit, then it

gives out the other superior alveolar nerves (middle and anterior):

2. Middle superior alveolar: usually provides sensory sensations to the premolars and the mesial root of the first molar.

3. Anterior superior alveolar: provides sensory sensations to the anterior teeth (canines and incisors).

II. The Facial Branches:

Infra-orbital: the terminal branch of the maxillary nerve provides sensation to the area or to the skin of the maxilla, upper lip and the labial mucosa and labial gingiva. (I.e. from the skin all the way deeply to the gingiva).

Zygomatico-facial and Zygomatico-temporal: both go to a small space on the lateral aspect of the skull, they are both branches of the maxillary nerve. Usually the maxillary nerve gives one zygomatic branch which divides later on to form Zygomatico-facial and Zygomatico-temporal, both of which pass through the zygomatic foramen on the lateral walls of the skull.

III. Pre-palatal branches:

Goes down through the pterygo-palatine fossa, through the palatal canal:

1. The anterior one goes to the hard palate and it’s called “greater palatine nerve”.

2. The other one goes to the soft palate and it’s called “lesser palatine nerve”.

3. The third one goes to the nasal septum, passing the septal wall of the nasal cavity and going all the way anteriorly to the incisive canal and it is called “incisive nerve” or “naso-palatine nerve”.

So in a quick review: The maxillary nerve (V3)

Goes out of the skull through foramen rotundum into the pterygopalatine fossa; there it divides to form the superior posterior alveolar nerve.

Then it goes to form the infra-orbital nerve which gives the middle and the anterior superior alveolar branches.

Also the maxillary nerve gives another branch which is the zygomatic nerve, which in turn divides into Zygomatico-facial and Zygomatico-temporal.

In addition to those two, in the face we have the continuation of the infra-orbital.

So we have three branches to the face, another three to the teeth, and the remaining ones to the palate: greater and lesser palatine.

Mandibular Nerve (V3):

It is a mixed nerve, as it contains the small motor root of the trigeminal nerve. So it has two functions: sensory and motor.

It usually provides general sensation to the skin over the mandible, to the anterior and superior part of the auricle (through auricular branch) and to the mental region (through the mental branch), and to the labial gingiva near it.

Motor innervations: those will be 8 muscles:

1- Muscles of mastication (4): Masseter, Temporalis, Lateral & Medial Pterygoids "the lateral pterygoids is the main opener of the moth if there is resistance".

2- The tensors (2): Tensor villi palatine and tensor tympani.

3- Mylohyoid and the anterior belly of digastric.

It goes out of the skull through foramen ovale as the main trunk, and then it goes into the infratemporal fossa, but just before it enters the infratemporal fossa it divides into: a small anterior division and a large posterior division.

The anterior small division has 4 branches; 3 motor and 1 sensory (buccal.nerve).

The posterior large division also has 4 branches; 1 motor (nerve to mylohyoid) and 3 sensory.

(The Doctor showed the divisions of the main trunk of the mandibular nerve on the slides).

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The main trunk (of the mandibular nerver) gives two branches:

First is a sensory nerve (the recurrent meningial nerve or as some books call it nervous spinosus, which is the more common name), it leaves the main trunk and goes along with the middle meningeal artery through foramen spinosum into the meninges (not as written in our textbook: foramen ovale, most of the time it’s foramen spinosum) it supplies the dura mater over the middle cranial fossa.

The other branch is nerve to medial pterygoid, it provides motor innervation to 3 muscles:

1. Medial pterygoid muscle.

2. Tensor villi palatini muscle.

3. Tensor tympani muscle.

Usually it gives out a communicating branch to hold the otic ganglion (the branch has nothing to do with the ganglion, it only holds it in its place.

Note: The otic ganglion gives synapse to parasympathetic innervation to the parotid gland.

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Branches of the Anterior Division:

“Please refer to your book about those branches”

1. Two deep temporal nerves: anterior and posterior.

2. Nerve to lateral Pterygoid.

3. Masseteric nerve.

4. Buccal nerve: which is the terminal branch of the anterior division of the mandibular nerve (this is the only sensory branch from the anterior division) "it give sensation to the cheek, buccal gingiva & to the skin over the buccinator muscle".

Masseteric nerve passes latterly above the lateral pterygoid muscle and through the mandibular notch, to reach the medial surface of the masseter muscle where it gives its motor innervation.

*Relations: (important)

Located superior to: lateral pterygoid muscle.

Anterior to: TMJ.

Posterior to: temporalis tendon (inserted into the coronoid process and anterior division of the mandible).

Buccal nerve passes laterally between the two heads of the lateral pterygoid muscle to reach the region of the cheek, specifically the region of the buccinator muscle. It is a sensory nerve; it gives sensation to: the skin and the infra-mandibular notch, cheeks and the buccal gingiva.

It joins another buccal nerve; a motor nerve, which is the buccal branch of the facial nerve which provides motor innervation to the buccinator muscle and the superior levator muscles.

(The Dr. shows the nerves and their locations on the slides)

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Branches of the posterior division:

A large division that contains three main nerves:

1. Lingual nerve: most anteriorly.

2. Posterior inferior alveolar.

3. auriculo-temporal nerve: most posteriorly.

Inferior alveolar has both motor and sensory innervations (mixed). It is sometimes referred to as the “inferior dental nerve”.

It descends through out the infratemporal fossa in between two structures: the spheno-mandibular ligament "prevent the excessive lateral movement" (sphenoid fossa to the lingual providing protection to this nerve) and the ramus of the mandible.

Then the nerve enters the mandibular canal through the mandibular foramen, and exits at about the level of the second premolar where it divides into: mental and incisive branches.

Mental branch leaves through mental foramen giving innervations towards the gingiva and cheeks.

The inferior alveolar nerve passes through the spheno-mandibular ligament and ramus of the mandible then it gives a motor branch (nerve

to mylohyoid muscle) before it enters the mandibular canal. Then it passes through the mandibular canal which is at the level of second premolar, and then gives the two sensory branches mental and incisive.

Nerve to mylohyoid descends through the mylohyoid groove of the mandible (you saw it in the lab, it’s a small linear groove just beneath the mylohyoid) then superficial to the submandibular gland, then it goes superiorly to the mylohyoid and anterior belly of digastric muscle which it innervates.

The Lingual nerve descends in front of the inferior alveolar – it is more anterior- then it goes over the lateral surface of medial pterygoid muscle & pass lateral to the hayogluosas muscle then medial to mandiblar 3rd molar where it usually joins the chorda tympani (from the facial nerve) at the lower border of the lateral pterygoid.

After that the nerve moves forward and medially just at the medial side of the mandibular third molar, and this is of high clinical importance because it can be injured in many cases when extracting the third molar "its function is general sensation of ant 2/3 of the tongue .

Note: the function of the chorda tympani is special sensation to the anterior 2/3s of the tongue and parasympathetic innervation to the

submandibular and sublingual salivary glands.

The auriculo-temporal nerve: it has two roots; from the posterior division of V3, both roots contain an important structure which is the middle meningeal artery, so they embrace this artery. Behind the artery they unite to form the auriculo-temporal nerve which passes backwards behind the middle meningeal artery; deep into the neck of the mandible. Then it turns upwards behind the TMJ along with the superficial temporal artery "this artery is more ant" and vein. Finally it ascends backwards.

Its function is giving general sensation to five areas:

1. TMJ.

2. Tympanic membrane (outside).

3. External auditory meatus.

4. Anterior 2/3s of the tongue. 5. Lateral aspect of the skull.

One other important function is carrying the postganglionic parasympathetic fibers from the lesser petrosal nerve of the Glossopharyngeal nerve to the parotid gland .

With that we finish this long epic with the trigeminal nerve…

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Was God's will and strengthTHE END

Done By:

The Prof

Mazen Mohammad Mosa Alamri

P.S : If there is any note write us @ the facebook page to the group or @ my page mazen m alamri .

Good luck.