Trigeminal nerve (CN V) - INFRATEMPORAL FOSSA

What type of fibres does the trigeminal nerve have?

The trigeminal nerve has motor fibres that innervate striated muscle derived from the 1st pharyngeal arch.

What are the three main branches of the trigeminal nerve?

V1 ophthalmic, V2 maxillary and V3 mandibular.

Which trigeminal branch carries the motor component?

V3 mandibular nerve.

What do the motor fibres of V3 innervate?

Muscles of mastication derived from the 1st pharyngeal arch.

Where is the temporal fossa located?

In the lateral portion of the cranium.

What are the boundaries of the temporal fossa?

Superior temporal line, inferior temporal line, zygomatic bone + supramastoid crest inferiorly, and zygomatic process of frontal bone anteriorly.

Where is the infratemporal fossa located?

Right beneath the temporal fossa.

What encloses the infratemporal fossa?

The mandible.

What are the medial and posterior boundaries of the infratemporal fossa?

Pterygoid plate and styloid process.

What is the anterior boundary of the infratemporal fossa?

Zygomatic bone + zygomatic process of maxilla.

What is the lateral boundary of the infratemporal fossa?

Zygomatic bone + zygomatic process of temporal bone.

Through what foramen does V3 exit?

Oval foramen.

What joint are the infratemporal fossa muscles associated with?

The temporomandibular joint.

What articulates in the TMJ?

The head/condylar process of the mandible articulates with the mandibular fossa and articular tubercle.

What helps the lack of congruency in the TMJ?

A fibrous articular disc.

What are the two main TMJ movements described?

Anterior movement for protrusion and downward movement for depression.

What is the trigeminal nerve?

The nerve of the 1st pharyngeal arch.

What sensory branches does the trigeminal nerve have?

V1, V2 and V3.

Where do the trigeminal branches exit from?

The trigeminal ganglion.

Where is the trigeminal ganglion housed?

In the trigeminal fossa.

What is special about the mandibular branch V3?

It is a sensory nerve accompanied by a motor branch.

Where does all of V3 exit?

Through the oval foramen.

What moves the TMJ?

Masticator muscles.

From which arch do masticator muscles derive?

1st pharyngeal arch.

Which nerve innervates masticator muscles?

Motor branches of CN V.

How many main muscles move the TMJ?

Four.

What is the masseter?

A very thick quadrangular muscle sitting on the mandible.

Where does the masseter originate?

From the zygomatic arch.

What are the two parts of the masseter?

Superficial and deep parts.

Where does the superficial masseter insert?

Along the inferior border of the zygomatic arch.

Where does the deep masseter insert?

Zygomatic arch, specifically the zygomatic process of the temporal bone.

What nerve innervates the masseter?

Masseteric nerve, a V3 motor branch.

What accompanies the masseteric nerve?

Blood vessels.

What lies posterior to the masseter?

The parotid gland.

What does the parotid duct do?

Passes anteriorly and pierces the buccinator to enter the mouth.

What is the temporal muscle?

A flat-shaped muscle that fills the temporal fossa.

What does the temporal muscle insert into?

The coronoid process of the mandible.

What type of tendon does temporalis have?

A very thick tendon passing into the infratemporal fossa.

What does temporal fascia do?

Prevents the temporalis muscle from bulging at the sides of the head during contraction.

What is the main action of temporalis?

Elevation/closing of the mandible.

What do deep posterior fibres of temporalis do?

Retract the mandible.

What is the medial pterygoid muscle shape?

Quadrangular, similar to the masseter.

Where does the medial pterygoid originate?

On the inner side of the mandible/mandibular angle region.

How many heads does the medial pterygoid have?

Two heads.

Where does the deep head of medial pterygoid insert?

Pterygoid fossa between the two laminae.

Where does the superficial head of medial pterygoid insert?

Maxillary tuberosity.

What ligament lies lateral/anterior to medial pterygoid?

Sphenomandibular ligament.

What does the sphenomandibular ligament connect?

Spine of sphenoid to angle of mandible.

What is the function of medial pterygoid?

Helps closure/elevation of the mandible.

How many heads does lateral pterygoid have?

Two heads.

Where does the lower head of lateral pterygoid insert?

Lateral aspect of the lateral pterygoid plate.

Where does the lower head of lateral pterygoid pass?

Between superficial and deep heads of the medial pterygoid.

Where does the upper head of lateral pterygoid insert?

Infratemporal crest.

Where do the two heads of lateral pterygoid originate?

Neck of the mandible, articular capsule and fibrous disc.

What happens when lateral pterygoid moves the mandibular head forward?

It also moves the disc with it.

Why does lateral pterygoid move the disc?

To maintain congruence of the TMJ.

What is the function of lateral pterygoid?

Lateral movement of the mandible and protrusion.

Which muscles in the floor of the mouth contribute to mastication and deglutition?

Mylohyoid and anterior belly of digastric.

What do mylohyoid and anterior belly of digastric do?

Depress the mandible.

What innervates mylohyoid and anterior belly of digastric?

Motor branch of the trigeminal nerve.

What innervates the posterior belly of digastric?

Facial nerve CN VII.

What is tensor veli palatini innervated by?

Motor branch of the trigeminal nerve.

What happens to the soft palate during mastication?

It becomes tense before deglutition.

What does tensor veli palatini do during mastication?

It gets the soft palate ready by tensing it.

What carries out protrusion of the mandible?

Mainly lateral pterygoid, assisted by medial pterygoid.

What carries out retraction of the mandible?

Mainly temporalis and deep part of masseter.

What carries out elevation of the mandible?

Temporalis, masseter and medial pterygoid.

What carries out depression of the mandible?

Muscles in the floor of the mouth plus gravity.

Into what trunks does V3 divide?

Anterior and posterior trunks.

Which V3 trunk is largely motor?

Anterior trunk.

What are the motor branches of the anterior trunk of V3?

Deep temporal nerves, nerve to lateral pterygoid, masseteric nerve, nerve to medial pterygoid, branch to tensor veli palatini and branch to tensor tympani.

What do deep temporal nerves innervate?

Temporal muscle from its deep aspect.

What does the nerve to lateral pterygoid innervate?

Lateral pterygoid muscle.

What does the masseteric nerve innervate?

Masseter from its deep aspect.

What does the nerve to medial pterygoid innervate?

Medial pterygoid muscle.

What does the branch to tensor veli palatini innervate?

Tensor veli palatini.

What does the branch to tensor tympani innervate?

Tensor tympani.

What does tensor tympani do?

Dampens movement of the tympanic membrane while chewing.

Why does tensor tympani tense the tympanic membrane?

To reduce its movement so it does not vibrate too much.

What motor branch comes from the posterior trunk of V3?

Nerve to mylohyoid.

What nerve does the nerve to mylohyoid travel with?

Inferior alveolar nerve.

Where does nerve to mylohyoid travel?

Along the mylohyoid sulcus.

What does nerve to mylohyoid innervate?

Mylohyoid and anterior belly of digastric.

Which V3 trunk is mostly sensory?

Posterior trunk.

What is the only sensory branch of the anterior trunk?

Buccal nerve.

What does the buccal nerve supply?

Mucosa of the oral cavity and skin of the cheeks.

What are the sensory branches of the posterior trunk?

Auriculotemporal nerve, inferior alveolar nerve and lingual nerve.

What does the auriculotemporal nerve surround?

The middle meningeal artery.

What does the auriculotemporal nerve supply in the TMJ?

The capsule of the temporomandibular joint.

What sensations does the auriculotemporal nerve carry from the TMJ?

Pressure, vibration and pain.

What regions does the auriculotemporal nerve supply?

Auricular and temporal regions.

What branch gives off the nerve to mylohyoid?

Inferior alveolar nerve.

Where does the inferior alveolar nerve enter?

Mandibular foramen.

Where does the inferior alveolar nerve course?

Through the mandibular canal.

What does the inferior alveolar nerve supply?

Sensory information from inferior teeth.

Where does inferior alveolar nerve exit distally?

Mental foramen.

What does the inferior alveolar nerve divide into?

Incisive nerve and mental nerve.

What does the mental nerve supply?

Skin of the chin.

What does the lingual nerve provide?

General sensory innervation to the mucosa of the anterior 2/3 of the tongue.

Does the lingual nerve carry taste?

No, general somatic sensory only.