Mandibular Nerve & Otic Ganglion

 MANDIBULAR  NERVE

• It is the largest of three divisions of trigeminal nerve.
• It is the nerve of first branchial arch.
• It is the mixed nerve consists of a large sensory and a small motor root.

ORIGIN

• Sensory root is derived from trigeminal ganglion.
• Motor root arises directly from motor nucleus in the pons and passes below the trigeminal ganglion.

COURSE  &  RELATIONS

From the middle cranial fossa both the roots emerge through foramen ovale

below the foramen they unite to form trunk of mandibular nerve in the infratemporal fossa

the trunk intervenes between the tensor veli palatini medially and lateral pterygoid laterally

otic ganglion is sandwiched between the nerve trunk and tensor veli palatini muscle

middle meningeal artery lies behind the trunk

then the trunk divides into a small anterior division and a large posterior division.

BRANCHES

From the Trunk :-

Nervous Spinosus (Meningeal Branch) –

• It enters the skull through the foramen spinosum along with the middle meningeal artery.
• It supplies the dura mater of middle cranial fossa.

Nerve to Medial Pterygoid –

• It supplies medial pterygoid muscle.
• Few fibres form the nerve pass through the otic ganglion without interruption and supply tensor tympani and tensor veli palatini muscles.

From the Anterior Division :-

• It gives off three motor branches and one sensory branch.

Masseteric Nerve –

• It passes laterally above the lateral pterygoid muscle.
• It runs behind the tendon of temporalis and in front of temporo-mandibular joint.
• It emerges through the mandibular notch along with the masseteric vessels.
• It supplies masseteric muscle from its deep surface.
• It also provides branches to temporo-mandibular joint.

Deep Temporal Nerves –

• They are usually two in number.
• They ascend deep to the lateral pterygoid muscle.
• They enter the deep surface of temporalis and supply the muscle.

Nerve to Lateral Pterygoid –

• It enters the deep surface of lateral pterygoid and supply the muscle.

Buccal Nerve –

• It is the only sensory branch of anterior division.
• It emerges between the two heads of lateral pterygoid muscle.
• Then appears on the cheek beneath the anterior border of masseter muscle.
• It supplies skin and mucous membrane of the cheek.

From the Posterior Division :-

• It gives off three sensory branches and few motor fibres.

Auriculo-temporal Nerve –

• It arises by two roots which encircle the middle meningeal artery.
• Then the roots unite to form a trunk which passes backward between neck of mandible and spheno-mandibular ligament.

It lies above the first part of maxillary artery

it turns laterally behind the temporo-mandibular joint

then it ascends deep to the upper part of parotid gland and behind the superficial temporal vessels

it enters the temporal region where it divides into superficial temporal branches.

• It receives communicating branches form otic ganglion which convey postganglionic secreto-motor fibres to the parotid gland.

It provides following branches –

• Auricular branches- they supply skin of tragus, upper part of auricle, roof and anterior wall of external acoustic meatus, cuticular layer of tympanic membrane.
• Superficial temporal branches- they supply the skin of temporal region.
• Articular branches- they supply temporo-mandibular joint.

Inferior Alveolar Nerve –

• It conveys both sensory and motor fibres.
• It emerges under the lateral pterygoid muscle and passes between the ramus of mandible and spheno-mandibular ligament.
• It enters the mandibular foramen accompanied by inferior alveolar vessels.
• Within the mandible the nerve runs in a bony canal and divides into incisive and mental nerves.

It provides following branches –

• Inferior dental plexus- supplies molar and premolar teeth, adjoining gum.
• Incisive nerve- it supplies the canine and incisor teeth, adjoining gum.
• Mental nerve- it emerges through the mental foramen and supplies skin of chin, lower lip.
• Mylohyoid nerve- it is a motor nerve arises before the inferior alveolar nerve enters the mandibular foramen, lodges in a groove on the ramus of mandible, appears in the digastric triangle, supplies mylohyoid and anterior belly of digastric muscles.
• Communicating branch- to the lingual nerve.

Lingual Nerve –

• It lies in the infratemporal fossa in front of inferior alveolar nerve.

It runs between the lateral pterygoid and tensor veli palatini muscles

receives chorda tympani nerve from behind at an acute angle

emerges from the lower order of lateral pterygoid muscle

passes downward and forward between the ramus of mandible and medial pterygoid muscle

then it comes in direct contact with mandible medial to the third molar tooth

here it is covered only by mucous membrane of the gum

it is palpable against the mandible about 1 cm below and behind the third molar tooth

it crosses the styloglossus and appears on the side of tongue resting on the hyoglossus

here the submandibular ganglion is suspended from the lingual nerve by two roots

then it winds round the lower border of submandibular duct from lateral to medial side

Finally, it reaches the dorsal surface of tongue.

It provides following branches –

• Sensory branches- to mucous membrane of anterior two third of the tongue (carry taste sensation), floor of the mouth and mandibular gum.
• Communicating branches- to chorda tympani nerve and submandibular ganglion which convey secreto-motor fibres to submandibular and sublingual glands.

APPLIED  ANATOMY

Referred Pain :-

• Pain from a disease of mandibular tooth or of the tongue is sometimes referred along the distribution of auriculo-temporal nerve to the ear and temporal region.
• Sometimes, lingual nerve is divided below and behind the last molar tooth to relieve intractable pain.

Nerve Block :-

• Occasionally, the mandibular nerve is blocked in trigeminal neuralgia by injecting local anaesthetic agent about 4 cm deep to the mandibular notch.

 

OTIC  GANGLION

• It is an oval, parasympathetic ganglion about 2-3 mm in size.

Situation :-

• It is situated in the infra-temporal fossa below the foramen ovale.
• It surrounds the origin of nerve to medial pterygoid muscle.
• Relations-
• Medially tensor veli palatini muscle
• Laterally trunk of mandibular nerve
• In front medial pterygoid muscle
• Behind middle meningeal artery

Connections :-

• Topographically, it is connected with mandibular nerve.
• Functionally, it is associated with glossopharyngeal nerve.

Roots :-

Parasympathetic / Motor Root –

• It is derived from the lesser petrosal nerve.
• The parasympathetic fibres arise from inferior salivatory nucleus of medulla.
• The fibres pass through-

tympanic branch of glossopharyngeal nerve

tympanic plexus

lesser petrosal nerve

Finally, reach the otic ganglion for relay.

Sympathetic Root –

• It is derived from a nerve plexus around the middle meningeal artery.
• It conveys post-ganglionic fibres from the superior cervical ganglion of sympathetic trunk.
• These fibres pass through ganglion without interruption.

Branches :-

• Post-ganglionic parasympathetic fibres- they join the auriculo-temporal nerve and supply secreto-motor fibres to parotid gland.
• Post-ganglionic sympathetic fibres- they pass through the ganglion without interruption, join the auriculo-temporal nerve and provide vaso-motor supply to parotid gland.