TRIGEMINAL NERVE
The trigeminal nerve, the largest cranial nerve (Fig 2.1), contains both
sensory and motor fibers. Genera...
The semilunar ganglion is developed from the neural crest. Like the
spinal ganglia it contains unipolar neurons. It is loc...
the thalamus these fibers continue on to the cerebral cortex. These fibers
convey pain and temperature from the entire tri...
Table 2.1: Outline of sensory, motor, and secretory nerve supply of certain
head regions.
Region Sensory nerves Secretory ...
Table 2.1: Outline sensory, motor, and secretory nerve supply of certain head
regions – cont’d.
Region Sensory nerves Secr...
afferent impulses from stretch receptors in the muscles of mastication. These
fibers are concerned with perfect synchroniz...
DIVISIONS OF THE TRIGEMINAL NERVE
Three large nerves proceed from the convex border of the semilunar
ganglion: ophthalmic ...
the skin of the lateral angle of the eye. It also transmits sensory impulses from
the sclera of the eyeball and the lining...
A. Supraorbital nerve
The supraorbital nerve is the largest branch of the frontal nerve. It
passes forward and leaves the ...
2. Long Ciliary Nerves: There are usually two or three long ciliary nerves
branching from the nasociliary nerve. They are ...
(2) Lateral Branches: These branches gives off twigs to the
mucous membrane of the anterior ends of the superior and middl...
C. Terminal branches of the ophthalmic division on the face
These terminal branches course below the trochlear nerve to su...
B. Sensory or long (postganglionic, sympathetic) root
The sensory fibers of the ciliary ganglion are derived from the
naso...
Maxillary division
The maxillary division of the trigeminal nerve (Fig 2.6) is entirely
sensory in function. The maxillary...
I. Branches given off in the middle cranial fossa
In the middle cranial fossa a small branch, the middle meningeal nerve,
...
The pterygopalatine nerves are two short nerve trunks that unite at the
pterygopalatine ganglion and are then redistribute...
The branches of distribution of the pterygopalatine nerves are divided
into three groups: orbital, nasal, and palatine.
1....
in an anterior direction between the osseous hard palate and the
mucoperiosteum to supply the major part of the hard palat...
In those bone, the nerve passes down the posterior or posterolateral wall
of the maxillary sinus, giving off sensory fiber...
Whether the maxillary bicuspids can be anesthetized by the infraorbital
injection or by the posterior superior alveolar in...
1. Inferior Palperbral Branches: Usually two or three in number, the
branches pass upward and supply sensory fibers to the...
Fibers of the great superficial petrosal nerve arise in the central nucleus,
which is called the superior salivatory nucle...
synapse within the ganglion. They continue on their way to the mucous
membrane of the nasal cavity and palate.
The pterygo...
(1) Posterior Superior Lateral Nerves: These nerves innervate the
mucosa over the posterior parts of the nasal conchae.
(2...
pterygopalatine canal. In the canal the palatine branches separate into these
strands: greater (anterior) palatine, middle...
d. Pharyngeal branch: This branch conveys sensory and secretory fibers
to the mucous membrane of the nasopharynx about the...
The sensory (afferent) root fibers are peripheral extensions of unipolar
cells located in the semilunar ganglion. The moto...
A. Nervus spinosus
The nervus spinosus arises outside the skull and then passes into the
middle cranial fossa to supply th...
A. Anterior divsion
The anterior division is smaller then the posterior division. It receives
sensory and motor fibers tha...
a. Anterior deep temporal nerve: This nerve passes upward and crosses
the infratemporal crest of the sphenoid bone. It end...
branches into the auriculotemporal, the lingual, and the inferior alveolar
nerves.
31
1. Auriculotemporal Nerve
The auriculotemporal nerve arises by a medial and a lateral root. These
roots embrace the middle...
c. Branches of the auriculotemporal nerve: The auriculotemporal nerve
divides into parotid, articular, auricular, meatal, ...
2. Lingual Nerve
The lingual nerve is the smaller of the two terminal branches of the
posterior division of the mandibular...
a. Communications of the lingual nerve with the chorda tympani branch of the
facial nerve: As the lingual nerve passes med...
Before the inferior alveolar nerve enters the mandibular foramen it
gives off a branch, the mylohyoid branch, which contai...
The preganglionic parasympathetic fibers enter the ganglion, and there
they synapse. Most of the postganglionic parasympat...
postganglionic fibers join the auriculotemporal nerve and with it go to the
parotid gland.
2. Sympathetic Root: The sympat...
3. Lacrimal nerve – Sensory from the skin of the upper eyelid and
lateral part of the eyebrow region; sensory from the con...
1. In the cranial cavity the maxillary division sends a
sensory branch to the dura.
2. In the pterygopalatine fossa he max...
(5) Nasopalatine branches – Sensory from the mucous membrane of
the lower and posterior part of the nasal septum and from ...
a) Inferior palpebral branches – Sensory from the skin of the
lower eyelid.
b) Lateral nasal branches – Sensory from the s...
d. Sensory from the skin lining the external
auditory meatus and from the lateral surface of the tympanic membrane.
e. Sen...
b. Mental nerve – Sensory from the skin of the
lower lip and chin regions and from the mucous membrane lining of the
lower...
The central processes of the previously mentioned branches of the
nerve send their impulses of pain and temperature backwa...
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The trigeminal nerve

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The trigeminal nerve

  1. 1. 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. 1
  2. 2. 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 2
  3. 3. 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 3
  4. 4. 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 V2 Inferior 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 V2 Superior labial nerve of infraorbital nerve of V2 Palatal side Greater palatine of V2 Nasopalatine of V2 Gingivae Lateral side Mandibular Long buccal nerve of V3 Mental nerve of V3 Lingual side Lingual nerve of V3 Mucus membrane of maxillary sainus Anterior, middle, posterior superior alveolar branches of V2 Mucous glands via sphenopalatine ganglion Greater superficial petrosal nerve of VII 4
  5. 5. 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 V2 Premaxillary portion nasopalatine V2 Mucous glands via sphenopalatine ganglion Greater 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 IX All others by cranial part of IX Floor of mouth Sensory branches of lingual nerve of V3 By submandibular ganglion from VII via chorda tympani 5
  6. 6. 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. 6
  7. 7. 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 7
  8. 8. 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. 8
  9. 9. 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. 9
  10. 10. 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. 10
  11. 11. (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. 11
  12. 12. 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. 12
  13. 13. 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. 13
  14. 14. 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). 14
  15. 15. 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 15
  16. 16. 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 gland Mucous 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 nerve Nasal 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. 16
  17. 17. 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 17
  18. 18. 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. 18
  19. 19. 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. 19
  20. 20. 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. 20
  21. 21. 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. 21
  22. 22. 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 22
  23. 23. 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. 23
  24. 24. (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 24
  25. 25. 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. 25
  26. 26. 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. 26
  27. 27. 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 27
  28. 28. 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. 28
  29. 29. 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 29
  30. 30. 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 30
  31. 31. branches into the auriculotemporal, the lingual, and the inferior alveolar nerves. 31
  32. 32. 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. 32
  33. 33. 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. 33
  34. 34. 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. 34
  35. 35. 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. 35
  36. 36. 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. 36
  37. 37. 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 37
  38. 38. 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. 38
  39. 39. 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 39
  40. 40. 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. 40
  41. 41. (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). 41
  42. 42. 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. 42
  43. 43. 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. 43
  44. 44. 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. 44
  45. 45. 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. 45

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