Download The mandibular nerve

Lecture 5
The mandibular nerve
This is the largest division of the trigeminal nerve and is the only one to
contain motor as well as sensory fibers. Developmentally, it is the nerve of
the first branchial arch and is thus responsible for supplying structures
derived from it . its sensory fibers supply the mandibular teeth and their
supporting structures, the mucosa of the anterior two-thirds of the tongue
and the floor of the mouth, the skin of the lower part of the face (including
the lower lip) and parts of the temporal region and auricle. Its motor fibers
supply the four muscles of mastication and the mylohyoid, anterior belly of
digastric, tensor veli palatine and tensor tympani muscles.
The mandibular nerve is formed in the infratemporal fossa by the union of
the sensory and motor roots immediately after they leave the skull at the
foramen ovale within the foramen ovale the motor root (or roots) lie
posteromedially to the sensory root and these root are accompanied by
emissary veins , the lesser petrosal nerve (from the glossopharyngeal nerve)
going to the otic ganglion and by the accessory meningeal artery . as the
mandibular nerve leaves the foramen ovale, it lies on the lateral pterygoid
muscle (slightly anterior to the neck of the mandible). After a short course,
the nerve divides into a smaller anterior trunk and a larger posterior trunk.
Before this division , the main trunk gives off two branches – the meningeal
branch and the nerve to medial pterygoid. The anterior trunk of the
mandibular nerve is mainly motor , the posterior trunk mainly sensory.
Branches
 Meningeal branch ( nervus spinosus)
 Nerve to medial pterygoid
 Anterior trunk:
Masseteric nerve
Nerve to lateral pterygoid
Buccal nerve
. posterior trunk:
Auriculotemporal nerve
Lingual nerve
Inferior alveolar nerve
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The meningeal branch of the mandibular nerve ( nervus
spinosus):
This arises from the main trunk of the mandibular nerve. It is a ' recurrent
nerve' as it rubs back into the middle cranial through the foramen
spinosum. It supplies the dura mater lining the middle and anterior
cranial fossae and the mucosa of the mastoid antrum and mastoid air
cells.
The nerve to the medial pterygiod muscle:
This enters the deep surface of the muscle and also gives slender
branches that pass uninterrupted through the otic ganglion to supply the
tympani and tensor veli palatine muscles.
The masseteric nerve
This is usually the first branch of the anterior trunk of the mandibular
nerve. It passes abve the upper border of the lateral pterygoid muscle (
accompanying the posterior deep temporal nerve ) and then crosses the
mandibular notch ( between the condylar and coronoid processes) to be
distributed into the masseter muscle. It also gives an articular branches.
The larger, lower trunk innervates the more superficial layers of the
masseter muscle .
The deep temporal nerve
These nerve also pass above the lateral pterygoid muscle. Anatomists
have provided varying descriptions for them. Anterior middle and
posterior deep temporal nerves may be recognized.
The nerve to the lateral pterygiod muscle
This may arise separately or may run with the buccal nerve before
entering the deep surface of the lateral pterygoid muscle .
The buccal branch of the mandibular nerve
This is the only sensory branch of the anterior trunk of the mandibular
nerve. On emerging between the upper and lower heads of the lateral
pterygoid muscle it passes downwards and forwards across the lower
head to contact the medial surface of the temporalis muscle as it inserts
onto the coronid process of the mandible. It then clears the ramus of the
mandible to lie on the lateral surface of the buccinator muscle gives
branches to the skin of the cheek before piercing the buccinator to supply
its lining mucosa, the buccal sulcus and the buccal gingiva related to the
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mandibular molar and in the buccal mucosa , these being post-ganglionic
fibres from the otic ganglion.
The buccal branch of the mandibular nerve may be seen to 'anastomose'
with the buccal branches of the facial nerve.
The auriculotemporal nerve
This is the first branch of the posterior of the mandibular nerve . it is
essentially sensory but also distributes autonomic fibers to the parotid
gland derived from the otic ganglion. It usually arises as two
roots(approx.. 75% of cases ) that encircle the middle meningeal artery
and unite behind the artery. The nerve then runs backwards under the
lateral pterygoid muscle to lie beneath the mandibular condyle(between
the condyle and the sphenomandibular ligament).
On entering the parotid region , it turns to emerge superficially between
the temporomandibular joint the external acoustic meatus. From the
upper surface of the parotid gland , the auriculotemporal ascends on the
side of the head with the superficial temporal vessels , passing over
theposterior part of the zygomatic arch, it gicse
it gives several branch es along its course:
 Ganglionic branches which communicate with the otic ganglion.
 Articular branches which enter the posterior part of the
temporomandibular joint; these carry proprioceptive information
important in mastication.
 Parotid branches which convey parasympathetic secretomotor
fibers and sympathetic fibers to the auriculotemporal nerve supply
the gland (with the exception of the capsule , which is innervated
by the great auricular nerve).
 Auricular branches ( usually two) which supply the tragus and crus
of the helix of the auricle , part of the external acoustic meatus ,
and the outer ( lateral ) surface of the tympanic membrane .
 Superficial temporal branches which are cutaneous nerve supplying
part of the skin of the temple.
The lingual nerve .
This is second branch of the posterior trunk of the mandibular nerve. It is
essentially a sensory nerve but , following union with the chorda tympani
branch of the facial nerve , it also contains parasympathetic fibers. Initially,
the nerve lies on the tensor veli palatine muscle deep to the lateral pterygoid
muscle . here , the chorda tympani nerve ( which has entered the
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infratemporal fossa via the petrotympanic fissure and passed over the spine
of the sphenoid bone ) joines the posterior surface of the lingual nerve .
emerging from the inferior border of the lateral pterygoid muscle , the
lingual nerve curves downwards and forwards in the space between the
ramus of the mandible and the medial pterygoid muscle (
pterygomsndibular space). At this level, it lies anterior to , and slightly
deeper than , the inferior alveolar nerve . the lingual nerve than leaves the
infratemporal fossa, passing downwards and forwards to lie close to the
lingual alveolar plate of
The mandibular third molar.befre curving forwads into the tongue, the
nerve is found above the origin of the mylohyoid muscle and lateral to the
hyoglossus muscle. The close relationship of the lingual nerve to the third
molar tooth makes the nerve susceptible to damage during removal of the
tooth. In addition , in about one in seven cases , the lingual is actually
located above the lingual bony plate in the third molar region and is liable
to damage during surgery .
The lingual nerve supplies the mucosa covering the anterior two-thirds of
the dorsum of the tongue, the ventral surface of the tongue, the floor of the
mouth and the lingual gingivae of two types: sensory and parasympathetic.
The sensory fibers are associated with taste for the anterior two- thirds of
the dorsum of the tongue. The parasympathetic fibers are preganglionic
fibers that pass to the submandibular ganglion . postganglionic fibers are
distributed to the submandibular and sublingual salivary glands.
The chorda tympani branch of the facial nerve
This is distributed through the lingual nerve and has two types of fibers.
Sensory fibers are associated with taste to the anterior two-thirds of the
tongue. Parasympathetic fibers are preganglionic to submandibular ganglion
postganglionic fibers are secret motor to the submandibular and sublingual
glands.
The inferior alveolar nerve
This is the largest branch of the mandibular division of the trigeminal nerve
. it is the third branch of the posterior trunk of the mandibular nerve.
Although it is essentially a sensory nerve , it also carries motor fibers
which are given off as the mylohyoid nerve . indeed the mylohyoid nerve
contains all the motor fibers of the posterior trunk of the mandibular nerve
.the inferior alveolar nerve descends deep to the lateral pterygoid muscle ,
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posterior to the lingual nerve in the pterygoid hiatus . here, it is crossed by
the maxillary artery . on emerging at inferior border of the mandible to enter
the mandibular foramen. It is accompanied in its course by inferior alveolar
blood vessels .
The mylohyoid nerve is given off just before the mandibular foramen. It
pierces the sphenomandibular ligament and runs in agroove ( the mylohyoid
groove) which lies immediately below the mandibular foramen . the
mylohyoid nerve may also contain sensory fibers that supply the skin of the
chin and medial parts of the submandibular triangle in the suprahyoid
region.
The main distribution of the inferior alveolar nerve is to the mandibular
teeth and their supporting structures , there being molar and incisive
branches, the mental nerve is a cutaneous branch that supplies the skin of
the chin and thee lower lip . it arises within the mandible in the premolar
region, but soon exits on onto the face via the mental foramen.
The otic ganglion
This parasympathetic ganglion immediately below foramen ovale on the
medial surface of the main trunk of the mandibular nerve . it is concerned
primarily with supplying the parotid gland. Like other parasympathetic
ganglia in the head, three types of fibers are associated with it:
parasympathetic , sympathetic and sensory fibers . however, only the
parasympathetic fibers synapse in the ganglion. The preganglionic
parasympathetic fibers originate from the inferior salivatory nucleus in the
brainstem. The fibers pass out in the glossopharyngeal nerve , appearing as
the lesser (superficial) petrosal branch of the facial nerve. The lesser
petrosal nerve usually enters the infratemporal fossa through the
sphenoptrosal nerve usually enters the infratemporal fossa through the
foramen ovale to join the otic ganglion. On occasion, the lesser petrosal
nerve passes through the sphenopetrosal fissure. The sympathetic root of
the otic ganglion is derived from postganglionic fibers from the superior
cervical ganglion.
They are said to reach the otic ganglion from the plexus od the middle
meningeal artery. Other description have it that the sympathetic root is
arises from the deep petrosal nerve or directly from the internal carotid
plexus . the sensory root is derived from the auriculotemporal nerve . the
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postganglionic parasympathetic fibers may also innervate the minor salivary
glands in the cheek, passing with the buccal branch of the mandibular nevre
The medial pterygoid by a branch that passes through the otic ganglion.
Clinical significance:
Lesions of mandibular division of trigeminal nerve will cause unilateral
paralysis of muscles of mastication followed by atrophy; results in a
sunken- in appearance along ramus of mandible and above the zygomatic
arch.
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