496
UNIT 3
Regulation and Integration of the Body
13
Infraorbital
nerve
Infraorbital
foramen
Supraorbital
foramen
Superior orbital fissure
Ophthalmic division (V
1
)
Trigeminal ganglion
Trigeminal nerve (V)
Maxillary division (V
2
)
Pons
Mandibular division (V
3
)
Foramen ovale
Foramen rotundum
Anterior trunk to
chewing muscles
Mandibular foramen
Mental foramen
Superior
alveolar
nerves
Lingual
nerve
Inferior alveolar
nerve
V
1
V
2
V
3
Temporalis
muscle
Medial
pterygoid
muscle
Lateral
pterygoid
muscle
Anterior
trunk of
mandibular
division (V
3
)
Masseter
muscle
Anterior belly of
digastric muscle
(a) Distribution of the trigeminal nerve
(c) Motor branches of the
mandibular division (V
3
)
(b) Distribution of sensory
fibers of each division
V Trigeminal Nerves
 
Ophthalmic division (V
1
)
Maxillary division (V
2
)
Mandibular division (V
3
)
Origin and course
Fibers run from face to pons
via superior orbital fissure.
Fibers run from face to pons via
foramen rotundum.
Fibers pass through skull via foramen
ovale.
Function
Conveys sensory impulses
from skin of anterior scalp,
upper eyelid, and nose, and
from nasal cavity mucosa,
cornea, and lacrimal gland.
Conveys sensory impulses from nasal
cavity mucosa, palate, upper teeth, skin
of cheek, upper lip, lower eyelid.
Conveys sensory impulses from anterior
tongue (except taste buds), lower teeth,
skin of chin, temporal region of scalp.
Supplies motor fibers to, and carries
proprioceptor fibers from, muscles of
mastication.
Clinical testing
Corneal reflex test: Touching
cornea with wisp of cotton
should elicit blinking.
Test sensations of pain, touch, and
temperature with safety pin and hot
and cold objects.
Assess motor branch by asking person
to clench his teeth, open mouth against
resistance, and move jaw side to side.
Homeostatic Imbalance
Trigeminal neuralgia
(nu-ral
9
je-ah), or
tic
douloureux
(tik doo
0
loo-roo
9
;
tic
5
twitch,
douloureux
5
painful), caused by inflammation of
trigeminal nerve, is widely considered to produce most excruciating pain known. The stabbing
pain lasts for a few seconds to a minute, but it can be relentless, occurring a hundred times
a day. Usually provoked by some sensory stimulus, such as brushing teeth or even a passing
breeze hitting the face. Thought to be caused by a loop of artery or vein that compresses
the trigeminal nerve near its exit from the brain stem. Analgesics and carbamazepine (an
anticonvulsant) are only partially effective. In severe cases, surgery relieves the agony—either
by moving the compressing vessel or by destroying the nerve. Nerve destruction results in loss
of sensation on that side of face.
Table 13.2
Cranial Nerves
(continued)
Largest cranial nerves; fibers extend from pons to face, and form
three divisions (
trigemina
5
threefold): ophthalmic, maxillary,
and mandibular divisions. As main general sensory nerves of face,
transmit afferent impulses from touch, temperature, and pain
receptors. Cell bodies of sensory neurons of all three divisions are
located in large
trigeminal ganglion.
The mandibular division also contains motor fibers that innervate
chewing muscles.
Dentists desensitize upper and lower jaws by injecting local
anesthetic (such as Novocain) into alveolar branches of maxillary and
mandibular divisions, respectively. Since this blocks pain-transmitting
fibers of teeth, the surrounding tissues become numb.
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