TRIGEMINAL NERVE

The trigeminal nerve, the largest cranial nerve (Fig 2.1), contains both

sensory and motor fibers. General somatic afferent fibers convey both

exteroceptive and proprioceptive impulses. Exteroceptive impulses of touch,

pain, and thermal senses are transmitted from the skin of the face and forehead

(Fig 2.2); mucous membranes of the nasal cavities, oral cavities, nasal sinuses,

and floor of the mouth; the teeth; the anterior two thirds of the tongue; and

extensive portions of the cranial dura. Proprioceptive impulses (deep pressure

and kinesthesis) are conveyed from the teeth, periodontium, hard palate, and

temporomandibular joint receptor. The nerve is also involved in conveying

afferent fibers from stretch receptors in the muscles of mastication. Special

visceral efferent fibers innervate the muscles, muscles of the eye, and facial

muscles. Afferent fibers constitute the sensory root (portio major), whereas the

efferent fibers form the smaller motor root (portio minor) (Fig 2.3).

The trigeminal nerve is attached to the lateral part of the pons by its two

roots, motor and sensory. The two roots enter the middle cranial fossa.

SENSORY ROOT OF THE TRIGEMINAL NERVE

The fibers of the sensory root of the trigeminal nerve arise from the

semilunar (gasserian) ganglion. They enter the brain stem through the side of

the pons.

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The semilunar ganglion is developed from the neural crest. Like the

spinal ganglia it contains unipolar neurons. It is located in Meckel’s cavity.

The ganglion is crescent shaped. The ganglion, with its unipolar neurons,

forms central and peripheral processes.

The peripheral branches form the ophthalmic, maxillary, and

mandibular divisions of the nerve. The central branches are the sensory roots

of the trigeminal nerve. These central branches leave the semilunar ganglion

and pass back and enter the pons, where they divide into ascending and

descending fibers.

The ascending fibers terminate in the upper sensory nucleus in the pons

lateral to the motor nucleus. The upper nucleus is the sensory (main) nucleus

of the trigeminal nerve. These ascending fibers convey light touch, tactile

discrimination, sense of position, and passive movement.

The upper or main nucleus gives rise to the dorsal trigeminothalamic

tract. The sensory fibers of this tack ascend upward. Most fibers cross to the

opposite side and accompany the medial lemniscus to the thalamus.

The spinal (bulbospinal) nucleus of the trigeminal nerve gives rise to

the ventral trigeminothalamic tract. The spinal nucleus extends caudally from

the main sensory nucleus to the second cervical segment. The fibers of the

ventral trigeminothalamic tract cross to the opposite side and ascend to the

thalamus. They form a loosely arranged bundle in the medial leminscus. From

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the thalamus these fibers continue on to the cerebral cortex. These fibers

convey pain and temperature from the entire trigeminal area. (Table 2.1 for an

outline of sensory, motor, and sectretory nerve supply of certain head regions).

MOTOR ROOT OF THE TRIGEMINAL NERVE

The motor root (Fig. 2.4) of the trigeminal nerve consists of fibers that

have their origin in the motor nucleus located in the upper pons. These

filaments pass from the pons, along the medial side of the semilunar ganglion.

The motor root then passes below to the foramen ovale, through which it

passes to joint the mandibular division immediately below the base of the

skull. The nerve is chiefly motor, ad its fibers supply the muscles of

mastication. It is often called the masticator nerve.

MESENCEPHALIC ROOT OF THE TRIGEMINAL NERVE

The mesencephalic root consists of afferent fibers that accompany the

fibers of the motor root. Entering the pons from the peripheral distribution of

the mandibular division of the trigeminal nerve, these fibers ascend to the

mesencephalic nucleus of the trigeminal nerve. This nucleus serves as an

afferent station that receives proprioceptive impulses from the

temporomandibular joint, the periodontal membrane, the maxillary and

mandibular teeth, and the hard palate. The mesencephalic nucleus also

receives

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Table 2.1: Outline of sensory, motor, and secretory nerve supply of certain head regions.

Region Sensory nerves Secretory Motor nerves

Upper lip Superior labial fibers of infraorbital nerve of V2

Buccal branches of VII

Corner of mouth Superior labial fibers of infraoral nerve of V2Inferior labial fibers of mental nerve of V3

Buccal and mandibular branches of VII

Lower lip Inferior labial fibers of mental nerve

Mandibular branch of VII

Cheek Long buccal nerve of V3 Buccal branches of VII

Teeth

Maxillary Posterior superior alveolar nerve of V2 to 6, 7, 8.Middle superior alveolar nerve of V2 to 4, 5 and mesiobuccal root of 6.Anterior superior alveolar nerve of V2 to 1,2,3.

Mandibular Inferior alveolar nerve of V3 to 1,2,3,4,5,6,7,8.

Gingivae Lateral side

Maxillary Posterior superior alveolar nerve of V2Superior labial nerve of infraorbital nerve of V2Palatal sideGreater palatine of V2Nasopalatine of V2

Gingivae Lateral side

Mandibular Long buccal nerve of V3Mental nerve of V3Lingual side Lingual nerve of V3

Mucus membrane of maxillary sainus

Anterior, middle, posterior superior alveolar branches of V2

Mucous glands via sphenopalatine ganglionGreater superficial petrosal nerve of VII

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Table 2.1: Outline sensory, motor, and secretory nerve supply of certain head regions – cont’d.

Region Sensory nerves Secretory Motor nerves

Hard palate Major portion greater palatine V2Premaxillary portion nasopalatine V2

Mucous glands via sphenopalatine ganglionGreater superficial nerve of VII

Soft palate Middle palatine nerve of V2 and palatine branches of IX

Same as for hard palate

Tensor palatine by V3 all others by cranial part of XI

Pharynx Pharyngeal branches of V2 and IX

Pharyngeal branch of sphenopalatine ganglion and by pharyngeal branches IX and X from pharyngeal plexus

Stylopharyngeal by IXAll others by cranial part of IX

Floor of mouth Sensory branches of lingual nerve of V3

By submandibular ganglion from VII via chorda tympani

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afferent impulses from stretch receptors in the muscles of mastication. These

fibers are concerned with perfect synchronization on controlling the biting

force of the jaws.

During mastication, proprioceptors in the muscles, tendons, periodontal

membrane, and joints send impulses through afferent fibers in the rigeminal

nerve that enter the brain stem, pass through the mesencephalic nucleus, and

synapse (first) in the main nucleus of the trigeminal nerve.

Secondary fibers cross the brain stem and ascend to the thalamus. The

secondary fibers constitute the dorsal trigeminothalamic fibers of the

bulbothalamic tract. They carry impulses of tactile perception from the afferent

fibers of the trigeminal nerve.

The third synapse occurs as these afferent fibers leave the thalamus and

proceed to the postcentral gyrus in the cortex (sensory).

These impulses permit awareness of motion in the jaws and the position

of the mandible and maxilla during chewing movements. Finally, some of the

proprioceptive impulses pass from the main sensory nucleus by means of the

secondary trigeminocerebellar fibers to the dentate and emboliform nuclei.

The cerebellium, in turn, conveys impulses to the motor cortex.

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DIVISIONS OF THE TRIGEMINAL NERVE

Three large nerves proceed from the convex border of the semilunar

ganglion: ophthalmic nerve, V1; maxillary nerve, V2; mandibular nerve, V3.

The ophthalmic nerve, or first division of the trigeminal nerve, is a

sensory nerve. It is the smallest of the three divisions, and passes forward and

enters the orbit through the superior orbital fissure.

The maxillary nerve, or second division of the trigeminal nerve, is a

sensory nerve. It begins at the middle of the semilunar ganglion and leaves the

skull through the foramen rotundum.

The mandibular nerve, the largest of the three divisions of the

trigeminal nerve, consists of two roots: a large sensory root arising from the

semilunar ganglion and a smaller motor root, which passes beneath the

ganglion to unite with the sensory root just after it emerges through the

foramen ovale.

Ophthalmic division

The ophthalmic division (Fig 2.5) is the smallest of the three branches

of the semilunar ganglion. It leaves the anterior medial part of the ganglion

and passes forward in the lateral wall of the cavernous sinus. Its fibers are

sensory, or afferent, from the scalp, the skin of the forehead, the upper eyelid

lining the frontal sinus, the conjuctiva of the eyeball, the lacrimal gland, and

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the skin of the lateral angle of the eye. It also transmits sensory impulses from

the sclera of the eyeball and the lining of the ethmoid cells. In the middle

cranial fossa, the nervus tentorii branches from the ophthalmic division to

supply the dura. The ophthalmic division also gives off communication

branches to the oculomotor, trochlear, and abducent cranial nerves.

As the ophthalmic division passes forward from the cavernous sinus, it

divides into three branches: lacrimal, frontal, and nasociliary nerves.

I. Lacrimal nerve

The lacrimal nerve is the smallest of the three branches. It passes into

the orbit at the lateral angle of the superior orbital fissure. It then courses in an

anterolateral direction to reach the lacrimal gland. Here it supplies sensory

fibers to the gland and adjacent conjuctiva.

In the orbit, postganglionic secretory fibers from the sphenopalatine

ganglion meet and travel along with he lacrimal nerve. These fibers are from

the zygomatic nerve.

II. Frontal nerve

The largest of the three branches, the frontal nerve, appears to be a

direct continuation of the ophthalmic division. It enters the orbit by way of the

superior orbital fissure. At about the middle of the orbit, the frontal nerve

divides into two branches: supraorbital and supratrochlear nerves.

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A. Supraorbital nerve

The supraorbital nerve is the largest branch of the frontal nerve. It

passes forward and leaves the orbit through the supraorbital foramen, or notch,

to supply the skin of the upper eyelid, the forehead, and the anterior scalp

region to the vertex of the skull.

B. Supratrochlear nerve

The smallest branch of the frontal nerve is the supratrochlear nerve. It

passes toward the upper medial angle of the orbit. Here it pierces the fascia of

the upper eyelid to supply the skin of the upper eyelid and lower medial

portion of the forehead.

III. Nasociliary nerve

The nasociliary nerve is the third main branch of the ophthalmic

division. It enters the orbit through the superior orbital fissure. Branches of the

nasociliary nerve are divided into those arising in the orbit, in the nasal cavity,

and on the face.

A. Branches in the orbit

1. Long Root Of The Ciliary Ganglion : The long, or sensory, root arises

from the nasociliary nerve. It contains sensory fibers, which pass

through the ganglion without synapsing and continue on to the eyeball

by means of the short ciliary nerves.

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2. Long Ciliary Nerves : There are usually two or three long ciliary nerves

branching from the nasociliary nerve. They are distributed to the iris

and cornea.

In addition, the long ciliary nerves contain postganglionic fibers, from

the superior cervical sympathetic ganglion.

3. Posterior Ethmoid Nerve : The posterior ethmoid nerve enters the

posterior ethmoid canal to be distributed to the mucous membrane

lining the posterior ethmoidal cells and the sphenoid sinus.

4. Anterior Ethmoid Nerve : The nasociliary nerve continues anteriorly

along the medial wall of the orbit. In its course, the anterior ethmoid

nerve gives off filaments that supply the mucous membrane of the

anterior ethmoid cells and frontal sinus. In the upper part of the nasal

cavity, the ethmoid nerve divides into two sets of anterior nasal

branches, the internal and external nasal branches.

a. Internal nasal branches: The internal nasal branches, in turn,

divide in the upper anterior part of the nasal cavity into two divisions.

(1) Medial or Septal Branches : These branches travel

downward to supply sensory innervation to the mucous membrane of that

area.

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(2) Lateral Branches : These branches gives off twigs to the

mucous membrane of the anterior ends of the superior and middle nasal

conchae and to the anterior lateral nasal wall.

b. External nasal branches: At the end border between the lower

edge of the nasal bone and the upper edge of the lateral nasal cartilage, the

external nasal branch passes externally to supply the skin over the tip of the

nose and the skin over the ala of the nose.

B. Branches arising in the nasal cavity

The branches of the nasociliary nerve that arise in the nasal cavity

supply the mucous membrane lining the cavity.

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C. Terminal branches of the ophthalmic division on the face

These terminal branches course below the trochlear nerve to supply

sensory fibers to the skin of the medial parts of both eyelids, the lacrimal sac,

and the lacrimal caruncle. These terminal fibers supply the skin over the side

of the bridge of the nose.

IV. Autonomic ganglion associated with the ophthalmic division of the trigeminal nerve.

These terminal branches course below the trochlear nerve to supply

sensory fibers to the skin of the medial parts of the both eyelids, the lacrimal

sac, and the lacrimal caruncle. These terminal fibers supply the skin over the

side of the bridge of the nose.

A. Motor or Short (preganglionic, parasympathetic) Root

These motor fibers arise from cells in the nucleus of Edinger-Westphal.

The oculomotor nucleus lies in the gray substance in the mesencephalon. The

axons of the autonomic nucleus course with the fibers of the oculomotor nerve

to the ciliary ganglion. They are the visceral efferent bundle that carries

preganglionic fibers to the ciliary ganglion.

In the ganglion, the preganglionic fibers synapse with postganglionic

fibers whose neurons form the short ciliary nerves that innervate the sphincter

pupillae and ciliary muscles of the iris.

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B. Sensory or long (postganglionic, sympathetic) root

The sensory fibers of the ciliary ganglion are derived from the

nasociliary nerve of the trigeminal nerve. This root also carries many

postganglionic fibers from cell bodies of the superior cervical sympathetic

ganglion. They join the nasociliary nerve. They pass through the ganglion

without synapse to innervate the radial fibers of the dilator pupillae muscle in

the iris.

C. Sympathetic root

As already mentioned, the sympathetic fibers may come from the

sensory root of the nasociliary nerve or direcly from the internal carotid

plexus. Short ciliary nerves emerge from the anterior border of the ciliary

ganglion and continue on to the posterior surface of the eyeball. Fibers of the

short ciliary nerves contain sensory, parasympathetic, and sympathetic fibers.

They run in theinner surface of the sclera toward the iris. The postganglionic

fibers of the parasympathetic group innervate the circular, or sphincter, muscle

fibers of the iris, which causes the pupil to constrict. They also innervate the

ciliary muscle, which changes the convexity of the crystalline lens.

Postganglionic fibers of the sympathetic group pass to the radial fibers of the

dilator pupillae muscle in the iris, which causes the pupil to dilate. The sensory

fibers are afferent from all parts of the eyeball and the conjunctiva.

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Maxillary division

The maxillary division of the trigeminal nerve (Fig 2.6) is entirely

sensory in function. The maxillary nerve originates at the middle of the

semilunar ganglion and continues forward in the lower part of the cavernous

sinus. It then passes to the foramen rotundum, through which it leaves the

cranial fossa and enters the pterygopalatine fossa. It enters the inferior orbital

fissure to pass into the orbital cavity. Here it turns laterally in a groove on the

orbital surface of the maxilla, called the infraorbital groove. Continuing

forward, the second division emerges on the anterior surface of the maxilla

through the infraorbital foramen, where it divides.

The maxillary division of the trigeminal nerve transmits sensory

(afferent) impulses from the lower eyelid, the side of the nose, and the upper

lip. It is sensory to all maxillary teeth and their gingivae, the mucous

membrane of most of the nasal cavity, the hard and soft palate regions, part of

the tonsillar region, and form the region of the pharynx near the opening of the

auditory (Eustachian) tube. In addition, afferent fibers arising in the mucous

membrane lining the maxillary sinus transmit sensory impulses by this

division of the fifth cranial nerve.

In its course from the semilunar ganglion, the maxillary division gives

off branches in four regions: in the middle cranial fossa, in the pterygopalatine

fossa, in the infraorbital groove and canal, and on the face (terminal branches).

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I. Branches given off in the middle cranial fossa

In the middle cranial fossa a small branch, the middle meningeal nerve,

passes with the middle meningeal artey and its branches to supply the dura

with sensory fibers

II. Branches in the pterygopalatine fossa

A. Zygomatic nerve

The zygomatic nerve leaves the second division in the pterygopalatine

fossa and passes anteriorly and laterally through the inferior orbital fissure into

the orbit. Here it divides into two parts: zygomaticofacial nerve and

zygomaticotermporal nerve.

1. Zygomaticofacial Nerve: The zygomaticofacial nerve passes forward on

the lateral orbital foramen. The nerve pierces the orbicularis oculi

muscle and supplies sensory fibers on the skin over the prominence of

the zygomatic bone.

2. Zygomaticotemporal Nerve: The zygomaticotemporal nerve leaves the

orbit between the great wing of the sphenoid and the zygomatic bone to

enter the temporal fossa. It supplies sensory fibers to the skin over the

anterior temporal fossa region.

B. Pterygopalatine (spehnopalatine) nerves

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The pterygopalatine nerves are two short nerve trunks that unite at the

pterygopalatine ganglion and are then redistributed into several branches. since

a great majority of the fibers in the trunks are trigeminal somatic afferent

fibers, which merely pass beside or through the ganglion without synapsing,

the branches are listed here as belonging to the maxillary nerve rather than the

pterygopalatine ganglion.

The pterygopalatine nerves also serve as important functional

communications between the ganglion and the maxillary nerve. Postganglionic

secretomotor fibers from the pterygopalatine ganglion pass by means of these

nerves back along the maxillary nerve to the zygomatic nerve, through which

they are routed to the lacrimal nerve and the lacrimal gland.

Table 2.2: Distribution of branches of the spnenopalatine ganglion.

Secretory to Sensory from

Lacrimal glandMucous glands of nasal region via

nasopalatine and posterior superior lateral nasal nerves.

Mucous glands of hard palate region by nasopalatine and greater palatine nerves.

Mucous glands of soft palate region by middle palatine nerve; also branches from pharyngeal plexus of IX and X.

Mucous membrane of pharynx by pharyngeal branch; also by IX and X.

Lacrimal gland, VI; lacrimal nerveNasal mucosa, V2 nasopalatine and

posterior superior lateral nasal branches.

Mucosa of hard palate by nasopalatine and greater palatine branches of V2.

Mucosa of soft palate by middle palatine branch of V2; also branches of pharyngeal plexus by IX and X.

Mucous membrane of pharynx by pharyngeal branch; also by IX and X.

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The branches of distribution of the pterygopalatine nerves are divided

into three groups: orbital, nasal, and palatine.

1. Orbital Branches: Two or three lines filaments enter the orbit by

means of the inferior orbital fissure and supply the periosteum of the orbit

and the mucous membrane of part of the posterior ethmoid cells and the

sphenoid sinus.

2. Nasal Branches: In the nasal cavity, the branches divide into the

posterior superior lateral branches and the medial or septal branch.

a. Posterior superior lateral nasal branches: These branches

transmit sensory impulses from the mucous membrane of the nasal

septum and posterior ethmoid cells.

b. Medial or septal branch: This branch passes downward and

forward. It transmits sensory impulses from the mucous membrane over

the vorner. It then descends in the incisal canal and ramifies in the

mucous membrane of the premaxillary region of the hard palate.

3. Palatine Branches: The palatine branches descend in the

pterygopalatine canal, where the fibers usually divide into three stands:

greater or anterior palatine, middle palatine, and posterior palatine.

a. Greater of anterior palatine nerve: This nerve emerges on the

hard palate by passing through the greater palatine foramen and courses

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in an anterior direction between the osseous hard palate and the

mucoperiosteum to supply the major part of the hard palate and the

palatine gingivae.

It breaks up into numerous branches in its course and finally

extends as far forward as the premaxillary palatine mucosa, which is also

supplied by terminal branches of the nasopalatine nerve.

b. Middle palatine nerve: This nerve emerges from the lesser

palatine foramen. Its fibers are sensory to the mucous membrane of the

soft palate.

c. Posterior palatine fibers: These nerve fibers, emerging from the

lesser palatine foramen, go to the mucous membrane of the tonsiller area

as part of the sensory supply to the tonsil itself.

C. Posterior superior alveolar braches

Two or three branches leave the maxillary division just before it enters

the inferior orbital fissure. They pass downward and continue on the posterior

surface of the maxilla. An internal branch of the posterior superior alveolar

nerve goes along with a branch of the internal maxillary artery through the

posterior superior alveolar canal, which opens on the posterior surface of the

maxilla.

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In those bone, the nerve passes down the posterior or posterolateral wall

of the maxillary sinus, giving off sensory fibers to the mucous membrane of

the sinus. It then supplies the maxillary molars and their gingivae. Within the

depths of the alveoli, or tooth sockets, some nerve filaments pass to supply the

periodontal membranes; whereas others, the pulpal fibers, pass through the

apical foramina of the roots of the molar teeth to supply the dental pulps.

D. Branches in the infraorbital groove and canal

The nerve in the infraorbital groove and canal becomes known as the

infraorbital nerve. From this groove serval fibers leave the infraorbital nerve

and descend.

1. Middle Superior Alveolar Nerve: The middle superior alveolar nerve

branches within the mucous membrane of the maxillary sinus to join with

other alveolar nerves in forming the superior dental plexus of nerves. In some

cases the middle superior alveolar nerve leaves the infraorbital nerve in the

posterior part of the floor of the infraorbital canal and passes in a downward

and anterior direction toward the apices of the maxillary bicuspids. In other

cases the middle superior alveolar nerve leaves the main trunk in the floor of

the infraorbital canal near the infraorbital foramen and passes downward in the

anterior or anterolateral wall of the sinus. Some authorities claim that the

middle superior alveolar nerve may be missing and that the maxillary

bicuspids receive their sensory innervation from the superior dental plexus.

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Whether the maxillary bicuspids can be anesthetized by the infraorbital

injection or by the posterior superior alveolar injection depends on the point

where the middle superior alveolar nerve leaves the infraorbital nerve. In some

cases infiltration anesthesia about the maxillary bicuspids may be necessary.

2. Anterior Superior Alveolar Nerve: The anterior superior alveolar nerve

descends from the infraorbital nerve just inside the infraorbital foramen in the

anterior part of the infraorbital canal. The anterior superior alveolar nerves

descend in fine canals in the maxilla to pass to the roots of the maxillary

central and lateral incisors and cuspid teeth. They also send connecting fibers

to the superior dental plexus of nerves within the maxilla. Fibers of the

anterior superior alveolar nerves also supply sensory innervation to the

mucous membrane of the anterior part of the maxillary sinus as well as the

labial gingivae of the incisors and cuspid teeth.

E. Terminal branches of the maxillary division on the face

As the infraorbital nerve is about to emerge from the infraorbital

foramen on the front of the maxilla, it divides into three terminal nerve

branches: the inferior palpebral, external or lateral nasal, and superior labial

branches.

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1. Inferior Palperbral Branches: Usually two or three in number, the

branches pass upward and supply sensory fibers to the skin of the lower

eyelid and its conjunctiva.

2. External or Lateral Nasal Branches: The external or lateral nasal

branches pass to the skin of the side of the nose.

3. Superior Labial Branches: Usually three or more in number, the

branches are distributed to the skin and mucous membrane of the upper lip.

III. Automic ganglion associated with the maxillary division of the trigeminal nerve

A. Sphenopalatine ganglion

The sphenopalatine ganglion is associated with the great superficial

petrosal nerve. It is a part of the seventh cranial nerve and is a parasympathetic

ganglion relaying chiefly secretomotor impulses from the nerve (Fig. 2.7). It

contains cell bodies of afferent taste fibers. The ganglion is stellate and lies

deep in the pterygopalatine fossa, suspended from the maxillary division of the

trigeminal nerve by two roots.

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Fibers of the great superficial petrosal nerve arise in the central nucleus,

which is called the superior salivatory nucleus. Form this nucleus, fibers pass

laterally and caudally and are joined by sensory fibers of the facial nerve to

form the intermediate nerve.

The facial nerve and the intermediate nerve cross the petrous part of the

temporal bone and traverse the facial canal. The canal curves, and at its sharp

curve, or genu, the intermediate nerve expands and becomes the geniculate

ganglion. From this ganglion preganglionic parasympathetic fibers leave as the

greater superficial petrosal nerve passes from the hiatus of the facial canal on

the anterior slope of the petrous portion to enter the middle cranial fossa. It

then passes anteriorly and medially beneath the semilunar ganglion of the

trigeminal nerve and passes through the foramen lacerum. At the lower end of

this foramen the greater superficial petrosal nerve is joined by the deep

petrosal nerve. The deep petrosal nerve is superficial petrosal and the deep

petrosal nerves are then called the nerve of the pterygoid canal, or vidian

nerve.

The vidian nerve passes through the pterygoid canal, to enter the

pterygopalatine fossa, to enter the sphenopalatine ganglion. This ganglion

hangs suspended from the maxillary nerve by two roots (pterygopalatine

neves). They contain sensory fibers from the maxillary nerve and do not

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synapse within the ganglion. They continue on their way to the mucous

membrane of the nasal cavity and palate.

The pterygopalatine nerve trunks are communications for the pterygopalatine

ganglion, since they are traversed by postganglionic fibers on their wayto the

maxillary nerve, which continue on their way to the mucous membrane of the

nasal cavity and palate.

The pterygopalatine nerve trunks are communications for the

pterygopalatine ganglion, since they are traversed by postganglionic fibers on

their way to the maxillary nerve, which continue to the lacrimal gland and

other glands of the nasal cavity and palate.

The sensory fibers pass through the ganglion, whereas the

parasympathetic fibers synapse in the ganglion.

1. Branches From The Sphenopalatine (Pterygopalatine)

Ganglion

a. Orbital branches: Orbital branches are made up of afferent fibers and

convey sensory or afferent impulses from the periosteum of the orbit.

Others supply the mucous membrane of the posterior ethmoid cells and the

sphenoid sinus.

b. Nasal branches: These nerves are divided into two groups: posterior

superior lateral nerves and nasopalatine (long sphenopalatine) nerve.

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(1) Posterior Superior Lateral Nerves : These nerves innervate the

mucosa over the posterior parts of the nasal conchae.

(2) Nasopalatine (Long Sphenopalatine) Nerve : The nasopalatine

nerve (Fig. 2.8) passes downward and forward between the periosteum

and the mucous membrane in the region of the vomer bone and, as it

continues downward and forward, reaches the floor of the nasal cavity. It

then descends in the incisal canal to appear in the anterior part of the hard

palate and supply the mucous membrane of the premaxilla.

c. Palatine branches (Fig. 2.9): From the sphenopalatine ganglion the

palatine branches descend in the pterygopalatine fossa and the

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pterygopalatine canal. In the canal the palatine branches separate into these

strands: greater (anterior) palatine, middle palatine, and posterior palatine.

(1) Greater or Anterior Palatine Nerve : This nerve emerges from the

greater palatine foramen in the region of the lateral margin of the palatine

bone and medial to the upper third molar. It then continues forward and

splits into numerous branches between the osseous roof of the oral cavity

and the mucoperiosteum. It carries sensory and secretory fibers to the

major part of the mucous membrane of the hard palate and palatal

gingivae. Its anterior terminal fibers extend forward as far as the

premaxillary palatine mucosa.

(2) Middle Palatine Nerve : This nerve emerges from a small

foramen in the medial aspect of the pyramidal part of the palatine bone to

supply sensory and secretory fibers to the mucosa membrane of the soft

palate.

(3) Posterior Palatine Nerve : This nerve usually emerges from a

lesser foramen posterior and slightly lateral to the middle palatine nerve.

The fibers of the posterior palatine nerve convey sensory and secretory

fibers to the mucous membrane in the tonsillar area.

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d. Pharyngeal branch: This branch conveys sensory and secretory fibers

to the mucous membrane of the nasopharynx about the opening of the

auditory tube.

e. Secretory fibers to the lacrimal gland: Preganglionic parasympathetic

fibers arising in the lacrimal nucleus pass to the geniculate ganglion and

then to the sphenopalatine ganglion. The sympathetic postganglionic fibers

from the deep petrosal nerve continue on through the ganglion.

From the sphenopalatine ganglion, the parasympathetic and the

sympathetic fibers pass back to the maxillary nerve and enter the zygomatic

nerve. They leave the zygomatic nerve in the orbit, join the lacrimal nerve, and

then go to the lacrimal gland to control its secretion.

Mandibular division

The mandibular division of the trigeminal nerve (Fig. 2.10) is the

largest of the three divisions. It is formed by the union of the large sensory

(afferent) bundle of fibers and a small motor (efferent) bundle of fibers.

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The sensory (afferent) root fibers are peripheral extensions of unipolar

cells located in the semilunar ganglion. The motor (efferent) root ribers are

derived from motor cells located in the medulla oblongata. These fibers

become incorporated with the sensory fibers in the mandibular trunk. The

large sensory root arises from the semilunar ganglion. Its fibers are distributed

to the dura, skin, and mucous membrane of the chin, cheek, and lower lip; the

external ear region; parotid gland; temporomandibular articulation; the scalp

over the region of the temporal bone; to the lower teeth and their gingivae; and

to the anterior two thirds of the tongue. The motor root innervates the muscles

of mastication. It supplies the temporal, internal and external pterygoid,

masseter, and mylohyoid muscles and the anterior belly to the diastric

muscles. Some of its fibers innervate the tensor veli palatini and the tensor

tympari muscles.

The motor root is located in the middle cranial fossa. It joins the

sensory root after the latter leaves the semilunar ganglion. The two roots pass

side by side in the dura of the middle cranial fossa to the foramen ovale.

Leaving the foramen ovale, the two roots unite to form a short single trunk.

The branches of the mandibular division may be divided into two

groups: branches from the undivided nerve and branches from the divided

nerve.

I. Branches from the undivided nerve

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A. Nervus spinosus

The nervus spinosus arises outside the skull and then passes into the

middle cranial fossa to supply the dura and the mastoid cells.

B. Nerve to internal pterygoid muscle.

A branch of the motor root passes to innervate the internal pterygoid

muscle. This branch passes without interruption to innervate the tensor veli

palatini and the tensor tympani muscles.

II. Branches from the divided nerve

Below the level of the undivided part of the mandibular division, the

trunk separates into two parts: anterior and posterior divisions.

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A. Anterior divsion

The anterior division is smaller then the posterior division. It receives

sensory and motor fibers that supply the muscles of mastication, the skin and

mucous membrane of the cheek, and the buccal gingivae and lower molars. It

passes downward and forward, where it divides:

1. Branch to external pterygoid muscle

2. Branch to masseter muscle

3. Branches to temporal muscles

a. Anterior deep temporal nerve

b. Posterior deep temporal nerve

4. Buccal (long buccal) nerve

1. Pterygoid nerve

The pterygoid nerve enters the medial side of the external pterygoid

muscle to provide its motor nerve supply.

2. Massetter nerve

The massetter nerve passes above the external pterygoid to traverse the

mandibular notch and enter the deep side of the massetter muscle.

3. Nerves to the Temporal Muscle

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a. Anterior deep temporal nerve: This nerve passes upward and crosses

the infratemporal crest of the sphenoid bone. It ends in the deep part of

the anterior portion of the temporal muscle.

b. Posterior deep temporal nerve: This nerve passes upward to the deep

part of the temporal muscle.

4. Buccal Nerve

Usually the buccal nerve passes downward, anteriorly and laterally

between the two heads of the external pterygoid muscle. At about the level of

the occlusal plane of the mandibular second and third molars, it divides several

branches that ramify on the buccinator muscle. It then sends fibers to the

mucous membrane of the cheek region. Other fibers distribute sensory

innervation to the skin of the cheek. These fibers are purely sensory. Still other

sensory fibers to the buccal gingivae about the mandibular molars and the

mucous membrane of the lower part of the buccal vestibule. The buccal nerve

occasionally contributes to the nerve supply of the second bicuspid and the

first molar of the lower jaw. Almost the entire mucosa of the cheek is supplied

by the buccal nerve.

B. Posterior division

The larger posterior division is mainly sensory but also carries some

motor components. This division extends downward and medially and then

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branches into the auriculotemporal, the lingual, and the inferior alveolar

nerves.

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1. Auriculotemporal Nerve

The auriculotemporal nerve arises by a medial and a lateral root. These

roots embrace the middle meningeal artery and unite behind the artery just

below the foramen spinosum. The united nerve passes posteriorly, deep to the

external pterygoid muscle, and then between the sphenomandibular ligament

and the neck of the condyle of the mandible. It traverses the upper deep part of

the parotid gland or its fascia and then crosses the posterior root of the

zygomatic arch. It passes with the superficial temporal artery in its upward

course and divides into numerous branches, to the tragus of the pinna of the

external ear, to the scalp about the ear, and as far upward as the vertex of the

skull.

a. Communications of the auriculotemporal nerve

(1) Two roots of the nerve : Each root receives communicating fibers from

the otic ganglion. These fibers are postganglionic, parasympathetic

secretory fibers that have come from the glossopharyngeal nerve by

way of the lesser superficial petrosal nerve. They control secretion of

the parotid gland.

(2) Communicating branches to the facial nerve : These fibers are purely

sensory from the auriculotemporal nerve.

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c. Branches of the auriculotemporal nerve: The auriculotemporal nerve

divides into parotid, articular, auricular, meatal, and terminal branches.

(1) Parotid branches : As the auriculotemporal nerve passes the

parotid gland, it gives off sensory, secretory, and vasomotor fibers to

the gland. The secretory fibers have passed as postganglionic

parasympathetic fibers to the gland. The vasomotor sympathetic

postganglionic fibers have accomplished the parasympathetic fibers to

the gland.

(2) Articular branches : One or two twigs of sensory fibers pass from

the auriculotemporal nerve and enter the posterior part of the

temporomandibular joint.

(3) Auricular branches : The anterior auricular branches are usually

two in number. They are sensory fibers supplying the skin of the helix

and tragus.

(4) Meatal branches : Two small branches usually supply the skin

lining the meatus and the tympanic membrane.

(5) Terminal branches : The major part of the filaments of the

auriculotemporal nerve pass to supply the scalp over the temporal

region.

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2. Lingual Nerve

The lingual nerve is the smaller of the two terminal branches of the

posterior division of the mandibular nerve. At first it passes medially to the

external pterygoid muscle and, as it descends, lies between the internal

pterygoid muscle and the ramus of the mandible in the pterygomandibular

space. It gives off small branches to the interior alveolar nerve that pass as

sensory fibers to part of the tonsil and mucous membrane of the posterior part

of the oval cavity.

In the pterygomandibular space the lingual nerve lies parallel to the

inferior alveolar nerve but medial and anterior to it. It then passes deep to

reach side of the base of the tongue. At the side of the tongue it lies below the

lateral lingual sulcus.

In the lateral lingual sulcus it is separated from the tongue by the

alveololingual groove. As it passes forward, it loops downward and medially

beneath the submandibular duct.

The lingual nerve contributes many sensory fibers to the mucous

membrane of the floor of the mouth and gingiva on the lingual surface of the

mandible. It occasionally supplies sensory fibers to the bicuspids and first

molar teeth.

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a. Communications of the lingual nerve with the chorda tympani branch of the

facial nerve: As the lingual nerve passes medially to the external pterygoid

muscle, it is jointed from behind by the chorda tympani nerve. This nerve

conveys secretory fibers from the facial nerve. The parasympathetic secretory

fibers control the submandibular and sublingual salivary glands. The secretory

fibers of the chorda tympani nerve fibers to the submandibular ganglion,

where they synapse. The secretory nerve fibers to the sublingual gland join in

a small branch from the submandibular ganglion to rejoin the lingual nerve

and pass with this nerve to the sublingual gland.

3. Inferior alveolar nerve

The inferior alveolar nerve is the largest of the branches of the posterior

division of the mandibular part of the trigeminal nerve. It passes downward on

the medial side of the external pteryoid muscle and the medial side of the

mandibular ramus. On the medial side of the ramus in the pterygomandibular

space, it enters the mandibular foramen. Within the mandible the inferior

alveolar nerve descends in the inferior alveolar canal and is distributed

throughout the body of the mandible. In the inferior alveolar canal it gives off

branches to the mandibular teeth as apical fibers that enter the apical foramina

of the lower teeth to supply the dental pulps. Some of the fibers are distributed

to the periodontal membrane of the various lower teeth.

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Before the inferior alveolar nerve enters the mandibular foramen it

gives off a branch, the mylohyoid branch, which contains sensory and motor

fibers. The mylohyoid nerve continues downward and forward in the

mylohyoid groove. It passes forward below the mylohyoid muscle, to which it

sends motor fibers, and it supplies motor fibers to the anterior belly of the

digastric muscle. There is some claim that a twig of sensory fibers of the

mylohyoid nerve may enter the mandible in the area of the chin to aid in the

sensory nerve supply to the mandibular incisors.

III. Autonomic ganglia associated with the mandibular division of the

trigeminal nerve.

Two ganglia are associated with the mandibular division (Fig. 2.10):

submandibular and otic ganglia.

A. Submandibular (Submaxillary) ganglion

The submandibular ganglion is a small ovoid body that is suspended

from the lingual nerve above the submandibular salivary gland. It is suspended

by two nerves from the lingual nerve. These parasympathetic fibers are

preganglionic, having their origins in the superior salivatory nucleus in the

medulla. They course within the intermediate nerve and in the facial canal and

group together to form the chorda tympani nerve. The chorda tympani nerve

continues down and forward to join the lingual nerve and passes with it to the

submandibular ganglion.

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The preganglionic parasympathetic fibers enter the ganglion, and there

they synapse. Most of the postganglionic parasympathetic fibers are short.

They supply secretory fibers to the submandibular gland. Other

parasympathetic fibers turn upward to rejoin the lingual nerve and pass with it

to the sublingual gland. The submandibular ganglion also receives

postganglionic sympathetic fibers from the plexus on the external maxillary

artery.

B. Otic ganglion

The otic ganglion is a flattened ovoid body located on the medial side

of the undivided mandibular division of the trigeminal nerve. It is below the

foramen ovale and in front of the middle meningeal artery. It has two main

roots: parasympathetic and sympathetic.

1. Parasympathetic Preganglionic (Secretory) Fibers: These parasympathetic

fibers arise in the inferior salivatory nucleus. This group of cells lies in the

floor of the fourth ventricle in the medulla. The efferent fibers pass by way to

the glossopharyngeal nerve through the jugular canal. Immediately below the

canal, they leave the nerve at its petrosal ganglion in the tympanic nerve

(Jacobson’s nerve) to pass into the middle ear region. The lesser superficial

petrosal nerve emerges from the tympanic plexus. Then it passes on the upper

surface of the petrous part to the foramen ovale. The lesser superficial petrosal

nerve is the parasympathetic root of the otic ganglion. In the otic ganglion the

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postganglionic fibers join the auriculotemporal nerve and with it go to the

parotid gland.

2. Sympathetic Root: The sympathetic root is made up of post ganglionic fibers

that have originated in the superior cervical sympathetic ganglion and the

plexus on the middle meningeal artery. These sympathetic fibers pass

uninterruptedly through the otic ganglion. With the postganlionic

parasympathetic fibers, they join the auriculotemporal nerve and, with its

glandular branches, continue to the parotid gland.

Afferent, or sensory, fibers from the parotid gland pass by way of the

auriculotemporal nerve.

Summary of Functions of the Trigeminal (Fifth Cranial) Nerve

A. Ophthalmic division

1. Supratrochlear nerve – Sensory from the medial part of the upper

eyelid and the lower medial part of the forehead; sensory from the

conjuctive of the upper eyelid.

2. Supraorbital nerve – Sensory from the skin of the upper eyelid

and the skin of the forehead and scalp as far back as the vertex of the

skull; sensory from the lining of the frontal sinus.

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3. Lacrimal nerve – Sensory from the skin of the upper eyelid and

lateral part of the eyebrow region; sensory from the conjunctiva of the

lateral part of the upper eyelid.

4. Nasociliary nerve

a. Long ciliary branch – Sensory from the eyeball and

ciliary ganglion.

b. Infratrochlear nerve – Sensory from the upper and lower

eyelids and from the side of the nose; sensory from the conjunctiva

and the lacrimal sac.

c. Ethmoid branches

(1) Anterior ethmoid branch – Sensory from the lining of the frontal

sinus and of the anterior ethmoid cells.

(2) Posterior ethmoid branches – Sensory from the lining of the

posterior ethmoid cells and the sphenoid sinus.

d. Internal branches – Sensory from the anterior portion of

the septum and lateral walls of the nasal cavity.

e. External nasal branch – Sensory from the tip of the

nose.

B. Maxillary division – Middle meningeal branch

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1. In the cranial cavity the maxillary division sends a

sensory branch to the dura.

2. In the pterygopalatine fossa he maxillary division gives

off two branches.

a. Zygomatic nerve and branches.

(1) Zygomaticofacial branch – Sensory from the skin over the

zygomatic bone.

(2) Zygomaticotemporal branch – Sensory from the skin of the side

of the forehead and of the anterior part of the temporal region.

b. Sphenopalatine nerves (pterygopalatine).

(1) Orbital branches – Sensory from the periosteum of the orbit and

from the lining of the sphenoid sinus and posterior ethmoid

cells.

(2) Greater palatine branch (anterior palatine) – Sensory from the

mucous membrane of the major part of the hard palate and

adjacent part of the soft palate.

(3) Lesser palatine branches – Sensory from the mucous membrane

of the soft palate and tonsil area.

(4) Posterior lateral nasal branches – Sensory over the nasal

conchae.

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(5) Nasopalatine branches – Sensory from the mucous membrane of

the lower and posterior part of the nasal septum and from the

premaxillary part of the hard palate.

(6) Pharyngeal branch – Sensory from the mucous membrane of the

nasopharynx and the area behind the auditory tube.

c. Posterior superior alveolar nerve.

(1) Gingival branches- Sensory from the buccal gingiva of the upper

molar region and from the mucous membrane of part of the

cheek.

(2) Alveolar branches – Sensory from the maxillary molars, except

the mesiobuccal root of the upper first molar and their gingivae,

and from the mucous membrane of the maxillary sinus.

(3) In the infraorbital canal region.

a) Middle superior alveolar nerve – Sensory from the

maxillary bicuspids and the mesiobuccal root of the first

molar; sensory from the lining of the maxillary sinsu.

b) Anterior superior alveolar nerve – Sensory from the

maxillary incisors and cuspid and from the lining of the

maxillary sinus.

(4) Terminal branches on the face (infraorbital branches).

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a) Inferior palpebral branches – Sensory from the skin of the

lower eyelid.

b) Lateral nasal branches – Sensory from the skin of the side

of the nose.

c) Superior labial branches – Sensory from the skin of the

upper lip.

C. Mandibular division

1. Nervus tentorii – Sensory from the dura of the

posterior cranial fossa and from the lining of the mastoid cells.

2. Buccal (long buccal) nerve – Sensory from the

mucous membrane and the skin of the cheek region; sensory from buccal

gingavae of the mandibular molar region.

3. Auriculotemporal nerve.

a. Sensory from the skin over the areas

supplied by the branches of the facial (VII) nerve, that is, zygomatic,

buccal, and mandibular areas.

b. Sensory from the perotid gland by means of

the parotid branch.

c. Sensory from the temporomandibular

articulation.

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d. Sensory from the skin lining the external

auditory meatus and from the lateral surface of the tympanic membrane.

e. Sensory from the skin and scalp over the

upper part of the external ear and the side of the head up to the vertex of

the skull.

4. Lingual nerve – Sensory from the mucous

membrane covering the anterior two thirds of the tongue; sensory from the

mucous membrane of the floor of the mouth and of the lingual side of the

mandibular gingivae; sensory from the submandibular and sublingual

glands and their ducts.

The lingual nerve conveys special sense of the taste from the anterior

two thirds of the tongue. It also contains secretomotor fibers to the

submandibular and sublingual salivary glands and the mucous glands in the

floor of the mouth.

5. Inferior alveolar nerve.

a. Dental branches – Sensory from all of the

lower molar and bicuspid (mandibular) teeth and their periodontal

membranes.

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b. Mental nerve – Sensory from the skin of the

lower lip and chin regions and from the mucous membrane lining of the

lower lip region.

c. Incisive nerve – Sensory from incisors,

cuspid teeth, and their periodontal membranes.

The trigeminal nerve has a distinct motor root that conveys efferent

fibers to muscles derived from the first branchial arch. The motor fibers join

with fibers of the mandibular and pass as:

1. Internal pterygoid nerve – Innervates the internal

pterygoid muscle, the tensor veli palatini muscle, and the tensor tympani

muscle.

2. Masseter nerve – Innervates the masseter muscle.

3. Deep temporal branches – Pass as the anterior and

posterior deep temporal branches to the temporal muscle.

4. External pterygoid nerve – Supplies the external

pterygoid muscle.

5. Mylohyoid nerve – Innervates the mylohyoid and the

anterior belly of the digastric muscles.

In passing from the neck to head the somatic sensory functions of the

cervical nerves are taken over by the trigeminal nerve.

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The central processes of the previously mentioned branches of the

nerve send their impulses of pain and temperature backward and downward

through the lateral part of the pons, forming the spinal tract of the trigeminal

nerve.

Those impulses subserving tactile sensibilities of the trigeminal nerve

pass to the semilunar ganglion and then into the main nucleus of the trigeminal

nerve located in the pons.

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