Temporal and Infratemporal Regions

TEMPORAL REGION

• The temporal region lies on either side of the head, above and anterior to the external acoustic meatus. It contains a shallow bony depression called the temporal fossa.

Temporal Fossa

– The temporal fossa is a depression on the lateral surface of the skull.

Boundaries

• Superiorly and posteriorly: It is bounded by the superior temporal line.
• Inferiorly: It is bounded by the zygomatic arch and infratemporal crest.
• Anteriorly: It is bounded by the frontal and zygomatic bones.
• Floor: It is formed by parts of four bones: Frontal, parietal, temporal, and greater wing of sphenoid.
• Roof: It is formed by the temporal fascia.
• Inferomedially: It communicates with the infratemporal fossa deep to the zygomatic arch.

Contents

1. Temporalis muscle.
2. Middle temporal artery.
3. Zygomaticotemporal nerve and accompanying vessels.
4. Deep temporal nerves supplying temporalis.
5. Deep temporal arteries arising from the maxillary artery.

INFRATEMPORAL FOSSA

• The infratemporal fossa is an irregular space situated below the skull base and zygomatic arch, deep to the ramus of mandible and lateral to the pharynx.
• It is not completely enclosed and communicates with several adjoining spaces, including the temporal and pterygopalatine fossae.

Boundaries

• Laterally: It is bounded by the ramus of mandible.
• Roof: It is formed mainly by the infratemporal surface of the greater wing of sphenoid.
• Medially: It is bounded by the lateral pterygoid plate.
• Anteriorly: It is bounded by the posterior surface of maxilla.
• Posteriorly: It is related to the styloid process and tympanic plate of temporal bone.
• Inferiorly: It is open and continuous with the tissue spaces of the upper neck.

Practical Note: Removal of the ramus of mandible provides access to the infratemporal fossa during dissection.

Communications

Superiorly

1. Foramen ovale: It communicates with the middle cranial fossa.
2. Foramen spinosum: It communicates with the middle cranial fossa.
3. Gap deep to zygomatic arch: It communicates with the temporal fossa.

Anteriorly

– Inferior orbital fissure: It communicates with the orbit.

Medially

– Pterygomaxillary fissure: It communicates with the pterygopalatine fossa.

Inferiorly

– It continues with the tissue spaces of the upper neck and communicates with the adjacent parapharyngeal region.

Contents of Infratemporal Fossa

1. Muscles

• Lateral pterygoid.
• Medial pterygoid.
• Tendon of temporalis.

2. Blood vessels

• Maxillary artery and its branches.
• Maxillary vein.
• Pterygoid venous plexus.

3. Nerves and ganglion

• Mandibular nerve and its branches.
• Chorda tympani nerve, a branch of the facial nerve.
• Otic ganglion.

MUSCLES OF MASTICATION

– The four principal muscles of mastication are:

1. Masseter.
2. Temporalis.
3. Medial pterygoid.
4. Lateral pterygoid.

Features of Muscles of Mastication

• Action: They produce movements of the mandible at the temporomandibular joints.
• Location: They occupy the temporal, parotid, and infratemporal regions.
• Insertion: They attach to different parts of the mandible. The lateral pterygoid also attaches to the articular disc and capsule of the temporomandibular joint.
• Nerve supply: All four muscles are supplied by branches of the mandibular nerve (V3).
• Development: They develop from the mesoderm of the first pharyngeal arch.

Masseter

• It is a powerful elevator of the mandible.
• It has a cruciate arrangement because its deeper fibres cross the superficial fibres obliquely.
• The middle and deep layers together form the deep part of the muscle.
• Its intramuscular tendinous septa produce ridges on the lateral surface of the mandibular ramus.
• The masseteric nerve and vessels pass through the mandibular notch to reach its deep surface.
• Trismus (lockjaw): Spasm of the muscles of mastication, particularly the masseter, restricts mouth opening. It is a characteristic feature of tetanus.

Practical Note: Removal of the parotidomasseteric fascia exposes the masseter muscle.

Temporal Fascia

• It is a strong aponeurotic sheet covering the temporalis muscle.
• Superior attachment: It attaches to the superior temporal line.
• Inferior attachment: It divides into superficial and deep layers that attach to the outer and inner margins of the zygomatic arch, respectively.
• Contents between the layers: These include fat, loose connective tissue, middle temporal vessels, and branches of the zygomaticotemporal nerve.

Temporalis

• It is a broad, fan-shaped muscle occupying the temporal fossa.
• Its fibres are arranged into three groups:
  • Anterior fibres: They descend vertically and elevate the mandible.
  • Middle fibres: They descend obliquely and assist in elevation of the mandible.
  • Posterior fibres: They run almost horizontally forwards and retract the protruded mandible.
• The deep temporal nerves and vessels lie between the muscle and the bony floor of the temporal fossa.

Medial Pterygoid

• It consists of superficial and deep heads, of which the deep head forms the greater part.
• It acts with the masseter to elevate the mandible.
• Bilateral contraction assists in protrusion of the mandible.
• Alternate contraction of the right and left medial pterygoid muscles produces side-to-side grinding movements during chewing.

Lateral Pterygoid

• It is a short, conical muscle with superior and inferior heads.
• Its fibres extend from the sphenoid bone towards the neck of the mandible and temporomandibular joint.
• The superior head is partly attached to the articular disc and joint capsule.
• The inferior head inserts mainly into the pterygoid fovea on the neck of the mandible.
• Bilateral contraction: It protrudes the mandible and assists in opening the mouth.
• Unilateral contraction: It moves the chin towards the opposite side, contributing to grinding movements.
• The articular disc is a fibrocartilaginous structure closely associated with the superior head of lateral pterygoid.

Relations of lateral pterygoid muscle

• The lateral pterygoid is a conical muscle with superior and inferior heads separated by a narrow gap.
• It is considered the key muscle of the infratemporal fossa because several important nerves and vessels are related to it.

Superficial Relations

– The following structures lie superficial to the muscle:

1. Masseter muscle.
2. Ramus of mandible.
3. Tendon of temporalis.
4. Second part of maxillary artery.

Deep Relations

– The following structures lie deep to the muscle:

1. Mandibular nerve.
2. Middle meningeal artery.
3. Sphenomandibular ligament.
4. Deep head of medial pterygoid.

Structures Related to Its Borders

• Upper border: The deep temporal and masseteric nerves emerge above the muscle.
• Lower border: The lingual nerve and inferior alveolar nerve and vessels emerge below the muscle. The middle and accessory meningeal arteries ascend deep to its lower border.
• Between the two heads: The buccal nerve passes between the heads. The maxillary artery may also pass through this gap as an anatomical variation.

Note: The pterygoid venous plexus surrounds the lateral pterygoid muscle.

Relations of medial pterygoid muscle

Superficial Relations

– The following structures lie lateral or superficial to the muscle:

1. Lateral pterygoid muscle.
2. Lateral pterygoid plate.
3. Lingual nerve.
4. Inferior alveolar nerve.
5. Ramus of mandible.

Deep Relations

– The following structures lie medial or deep to the muscle:

1. Tensor veli palatini.
2. Levator veli palatini.
3. Superior constrictor of pharynx.
4. Stylopharyngeus.
5. Styloglossus.
6. Styloid process.

MAXILLARY ARTERY

– The maxillary artery is the principal artery supplying the deep structures of the face and infratemporal region.

Beginning

– It arises as a terminal branch of the external carotid artery within the parotid gland, behind the neck of the mandible.

Course

– The lateral pterygoid muscle divides the maxillary artery into three parts:

• First part (mandibular): It passes forwards from the neck of the mandible towards the inferior border of lateral pterygoid.
• Second part (pterygoid): It runs upwards and forwards, either superficial or deep to the inferior head of lateral pterygoid.
• Third part (pterygopalatine): It enters the pterygopalatine fossa through the pterygomaxillary fissure.

Branches of Maxillary Artery

First part (five branches)

1. Deep auricular artery.
2. Anterior tympanic artery.
3. Middle meningeal artery.
4. Accessory meningeal artery.
5. Inferior alveolar artery.

Second part (four groups of muscular branches)

1. Masseteric artery.
2. Deep temporal arteries.
3. Pterygoid branches.
4. Buccal artery.

Third part (six branches)

1. Posterior superior alveolar artery.
2. Infraorbital artery.
3. Descending palatine artery.
4. Pharyngeal artery.
5. Artery of pterygoid canal.
6. Sphenopalatine artery.

BRANCHES OF FIRST PART

Deep Auricular Artery

• It ascends to enter the external acoustic meatus through small foramina in its floor.
• It supplies the skin of the external acoustic meatus, outer surface of the tympanic membrane, and temporomandibular joint.

Anterior Tympanic Artery

• It passes through the petrotympanic fissure to enter the tympanic cavity.
• It supplies the inner surface of the tympanic membrane and adjoining middle ear structures.

Middle Meningeal Artery

• It is the largest branch of the first part of the maxillary artery.
• It ascends deep to lateral pterygoid and is encircled by the two roots of the auriculotemporal nerve.
• It enters the middle cranial fossa through the foramen spinosum, accompanied by the meningeal branch of mandibular nerve.
• Within the cranial cavity, it divides into anterior and posterior branches supplying the dura mater.
• Clinical significance: The anterior branch passes deep to the pterion and may rupture following a skull fracture, producing an epidural haematoma.

Accessory Meningeal Artery

• It ascends deep to lateral pterygoid and usually enters the middle cranial fossa through the foramen ovale.
• It supplies the meninges and adjoining structures of the infratemporal fossa.

Inferior Alveolar Artery

• It descends with the inferior alveolar nerve and enters the mandibular foramen to supply the mandible and lower teeth.
• Its detailed course and branches are described below.

BRANCHES OF SECOND PART

– All branches of the second part are primarily muscular.

Deep Temporal Arteries

• The anterior and posterior deep temporal arteries ascend between temporalis and the floor of the temporal fossa.
• They supply the temporalis muscle.

Pterygoid Branches

– They supply the medial and lateral pterygoid muscles.

Masseteric Artery

• It passes laterally through the mandibular notch and enters the deep surface of masseter.
• It supplies the masseter muscle and adjoining structures.

Buccal Artery

– It accompanies the buccal nerve and supplies the buccinator muscle and adjacent cheek tissues.

BRANCHES OF THIRD PART

Posterior Superior Alveolar Artery

• It usually arises near the pterygomaxillary fissure and divides into two or three branches.
• These branches enter the posterior superior alveolar foramina on the posterior surface of maxilla.
• Distribution: It supplies the maxillary molar teeth, adjoining gingiva, and mucosa of the maxillary sinus.

Infraorbital Artery

• It enters the orbit through the inferior orbital fissure and runs forwards through the infraorbital groove and canal.
• It emerges onto the face through the infraorbital foramen, accompanied by the infraorbital nerve.

Branches

• Orbital branches: They supply adjoining orbital structures.
• Middle superior alveolar artery: When present, it supplies the maxillary premolar teeth.
• Anterior superior alveolar artery: It supplies the upper canine and incisor teeth and adjoining maxillary sinus.
• Facial branches: They supply the lower eyelid, lacrimal sac region, lateral nose, and upper lip.

Descending Palatine Artery

• It descends through the greater palatine canal and divides into greater and lesser palatine arteries.
• Greater palatine artery: It emerges through the greater palatine foramen and runs forwards along the hard palate. It enters the nasal cavity through the incisive canal.
• Lesser palatine arteries: They emerge through the lesser palatine foramina and supply the soft palate and adjoining tonsillar region.
• Distribution: These arteries supply the hard palate, palatal gingiva, soft palate, and adjacent mucosa.

Pharyngeal Artery

• It passes backwards through the palatovaginal (pharyngeal) canal.
• It supplies the nasopharynx, auditory tube, and adjoining structures.

Artery of Pterygoid Canal

• It passes backwards through the pterygoid canal.
• It supplies the upper pharynx, auditory tube, and adjacent tissues.

Sphenopalatine Artery

• It is the terminal continuation of the maxillary artery.
• It enters the nasal cavity through the sphenopalatine foramen.

Terminal branches

• Posterior lateral nasal branches: They supply the lateral nasal wall and adjoining paranasal sinuses.
• Posterior septal branches: They supply the nasal septum.

Inferior alveolar or dental artery

• The inferior alveolar artery arises from the first part of the maxillary artery.
• It is the principal arterial supply to the mandibular teeth and adjoining bone.

Course

• It descends between the sphenomandibular ligament and ramus of mandible, accompanied by the inferior alveolar nerve and vein.
• It enters the mandibular foramen and passes forwards through the mandibular canal.

Termination

• Mental branch: It emerges through the mental foramen and supplies the chin and lower lip.
• Incisive branch: It continues forwards within the mandible to supply the lower canine and incisor teeth.

Branches

• Lingual branch: When present, it supplies the lingual gingiva and adjacent tissues.
• Mylohyoid branch: It arises before the artery enters the mandibular foramen and accompanies the mylohyoid nerve along the mylohyoid groove. It supplies mylohyoid and adjoining structures.
• Dental branches: They supply the mandibular molar and premolar teeth, surrounding alveolar bone, and gingiva.

PTERYGOID PLEXUS OF VEINS

• The pterygoid venous plexus is a network of veins situated around and within the lateral pterygoid muscle.
• It drains into the maxillary vein, which forms at the posterior end of the plexus.

Communications

• Inferior ophthalmic vein: It communicates through the inferior orbital fissure.
• Cavernous sinus: It communicates through emissary veins passing through foramina at the skull base.
• Facial vein: It communicates through the deep facial vein.

Functional and Clinical Significance

• Venous pump: Contraction of the lateral pterygoid compresses the plexus and helps propel blood towards the maxillary vein.
• Spread of infection: Its valveless venous communications provide a potential route for the spread of facial and orbital infections to the cavernous sinus, occasionally causing cavernous sinus thrombosis.

MAXILLARY VEIN

– The maxillary vein is a short vein accompanying the first part of the maxillary artery.

Formation

– It forms by the union of veins from the pterygoid venous plexus near the inferior border of the lateral pterygoid.

Course

– It passes backwards between the sphenomandibular ligament and neck of the mandible, accompanying the first part of the maxillary artery.

Termination

– It joins the superficial temporal vein within the parotid gland to form the retromandibular vein.

MANDIBULAR NERVE

• The mandibular nerve (V3) is the largest division of the trigeminal nerve and contains both sensory and motor fibres.
• It is the nerve of the first pharyngeal arch.

Course and Relations

• Origin: It arises through two roots:
  • Sensory root: It arises from the trigeminal ganglion.
  • Motor root: It arises from the motor nucleus of trigeminal nerve in the pons.
• The smaller motor root passes deep to the trigeminal ganglion and sensory root.
• Both roots pass through the foramen ovale and unite immediately below it to form the main trunk.
• Relations: The nerve lies in the infratemporal fossa, deep to lateral pterygoid and lateral to tensor veli palatini.
• Termination: It divides into a smaller anterior division and larger posterior division.

Practical Note: Careful removal of the superior head of lateral pterygoid exposes the main trunk of the mandibular nerve.

Branches of Mandibular Nerve

A. Branches from the main trunk

1. Meningeal branch (nervus spinosus).
2. Nerve to medial pterygoid, which also gives branches to tensor veli palatini and tensor tympani.

B. Branches from the anterior division

• Three motor branches:
  • Masseteric nerve.
  • Deep temporal nerves.
  • Nerve to lateral pterygoid.
• One sensory branch: 4. Buccal nerve.

C. Branches from the posterior division

1. Auriculotemporal nerve: It supplies the temporal region, parts of the auricle, external acoustic meatus, and temporomandibular joint. It also carries secretomotor fibres to the parotid gland.
2. Lingual nerve: It carries general sensation from the anterior two-thirds of the tongue. Through chorda tympani, it also carries taste fibres and parasympathetic fibres destined for the submandibular and sublingual glands.
3. Inferior alveolar nerve: It supplies the mandibular teeth and gives the nerve to mylohyoid, mental nerve, and incisive branch.

BRANCHES FROM THE MAIN TRUNK

Meningeal Branch (Nervus Spinosus)

• It is a small recurrent branch that enters the middle cranial fossa through the foramen spinosum, accompanying the middle meningeal artery.
• It supplies the dura mater of the middle cranial fossa.

Nerve to Medial Pterygoid

• It arises from the medial aspect of the main trunk and supplies the medial pterygoid.
• It also gives branches to tensor veli palatini and tensor tympani, which pass through the otic ganglion without synapsing.

BRANCHES FROM THE ANTERIOR DIVISION

Masseteric Nerve

• It passes laterally above the superior border of lateral pterygoid.
• It crosses the mandibular notch, anterior to the temporomandibular joint, and enters the deep surface of masseter.
• Distribution: It supplies masseter and contributes articular fibres to the temporomandibular joint.

Practical Note: Reflection of masseter from its origin exposes the masseteric nerve and vessels.

Deep Temporal Nerves

• These are usually anterior and posterior branches that emerge above the superior border of lateral pterygoid.
• They ascend along the infratemporal crest and enter the temporal fossa with the deep temporal vessels.
• Distribution: They enter the deep surface of temporalis and supply the muscle.

Nerve to Lateral Pterygoid

– It is a short motor branch that enters the deep surface of lateral pterygoid and supplies the muscle.

Buccal Nerve

• It is the principal sensory branch of the anterior division of mandibular nerve.
• It usually passes between the two heads of lateral pterygoid before descending towards the cheek.
• Distribution: It supplies the skin and mucosa of the cheek and the buccal gingiva of mandibular molar teeth.

Note: The buccal nerve is sensory. The buccinator muscle receives motor supply from the buccal branches of the facial nerve.

BRANCHES FROM THE POSTERIOR DIVISION

Auriculotemporal Nerve

• The auriculotemporal nerve is predominantly sensory and arises by two roots from the posterior division of mandibular nerve.
• The two roots encircle the middle meningeal artery before uniting into a single nerve.
• It passes backwards deep to lateral pterygoid and behind the neck of mandible.
• It curves around the posterior aspect of the temporomandibular joint and ascends over the root of the zygomatic arch into the temporal region.

Branches and Distribution

• Communicating branch: It receives postganglionic parasympathetic fibres from the otic ganglion and conveys them to the parotid gland.
• Auricular branches: They supply the tragus, part of the auricle, external acoustic meatus, and outer surface of the tympanic membrane.
• Superficial temporal branches: They provide sensory innervation to the skin of the temporal region.
• Articular branches: They supply the temporomandibular joint.

Inferior alveolar nerve

• The inferior alveolar (dental) nerve is a branch of the posterior division of the mandibular nerve.
• It is a mixed nerve, carrying sensory and motor fibres.

Course

• It emerges below the inferior border of lateral pterygoid and descends between the ramus of mandible laterally and sphenomandibular ligament medially.
• It enters the mandibular foramen with the inferior alveolar vessels and runs forwards through the mandibular canal.
• Near the mental foramen, it divides into mental and incisive branches.

Branches

1. Nerve to mylohyoid: It arises before the inferior alveolar nerve enters the mandibular foramen. It runs forwards in the mylohyoid groove and supplies mylohyoid and the anterior belly of digastric.
2. Dental branches: They supply the mandibular molar and premolar teeth and adjoining supporting tissues.
3. Mental nerve: It emerges through the mental foramen and supplies the skin of the chin, lower lip, and labial gingiva.
4. Incisive branch: It continues within the mandible and supplies the canine and incisor teeth and adjoining tissues.

Lingual nerve

– The lingual nerve is a sensory branch of the posterior division of the mandibular nerve.

Course

• It descends between lateral pterygoid laterally and tensor veli palatini medially, anterior to the inferior alveolar nerve.
• The chorda tympani nerve joins it at an acute angle below the skull base.
• It emerges below lateral pterygoid and passes forwards between the mandibular ramus and medial pterygoid.
• It lies close to the inner surface of the mandible near the third molar tooth, where it is covered mainly by oral mucosa.
• It crosses styloglossus and runs forwards on the lateral surface of hyoglossus.
• It loops beneath the submandibular duct, passes onto the lateral surface of genioglossus, and divides into terminal branches.

Branches

• General sensation: It supplies the anterior two-thirds of the tongue, floor of the mouth, and lingual gingiva of mandibular teeth.
• Taste sensation: It carries taste fibres from the anterior two-thirds of the tongue, except the circumvallate papillae, through the chorda tympani.
• Secretomotor fibres: It conveys preganglionic parasympathetic fibres from chorda tympani to the submandibular ganglion for the submandibular and sublingual glands.

Chorda tympani nerve

– The chorda tympani is a branch of the facial nerve (CN VII) that carries taste and preganglionic parasympathetic fibres.

Beginning

– It arises from the facial nerve within the facial canal, approximately 6 mm above the stylomastoid foramen.

Course

• It enters the middle ear through the posterior canaliculus for chorda tympani.
• Within the tympanic cavity, it crosses the medial surface of the tympanic membrane between the malleus and incus.
• It leaves the middle ear through the anterior canaliculus and petrotympanic fissure to enter the infratemporal fossa.
• It passes downwards and forwards deep to lateral pterygoid and joins the lingual nerve at an acute angle.

Functional components Viva, MCQ

• Special visceral afferent fibres: They carry taste sensations from the anterior two-thirds of the tongue, excluding the circumvallate papillae.
• General visceral efferent fibres: They carry preganglionic parasympathetic impulses to the submandibular ganglion for secretion by the submandibular and sublingual glands.

Otic ganglion

• The otic ganglion is a small, oval parasympathetic ganglion, measuring approximately 2–3 mm.
• Location: It lies in the infratemporal fossa, immediately below the foramen ovale.
• Topographical connection: It is associated with the mandibular nerve.
• Functional connection: It receives preganglionic parasympathetic fibres originating from the glossopharyngeal nerve.

Relations

• Laterally: Main trunk of mandibular nerve.
• Medially: Tensor veli palatini.
• Anteriorly: Middle meningeal artery.
• Posteriorly: Medial pterygoid muscle.

Roots and Connections

1. Parasympathetic (secretomotor) root

• Preganglionic fibres: They arise from the inferior salivatory nucleus and travel through the glossopharyngeal nerve, its tympanic branch, tympanic plexus, and lesser petrosal nerve.
• The lesser petrosal nerve enters the middle cranial fossa and usually passes through the foramen ovale to reach the otic ganglion, where its fibres synapse.
• Postganglionic fibres: They join the auriculotemporal nerve and reach the parotid gland to stimulate salivary secretion.

2. Sympathetic root

• Preganglionic fibres arise mainly from the T1 spinal segment and ascend through the sympathetic trunk to the superior cervical ganglion, where they synapse.
• Postganglionic fibres reach the otic ganglion through the periarterial plexus around the middle meningeal artery.
• These fibres pass through the ganglion without synapsing and provide vasomotor innervation.

3. Sensory root

• Sensory fibres from the auriculotemporal nerve pass through the ganglion without synapsing.
• They convey general sensation from the parotid gland.

4. Motor root

• Motor fibres from the nerve to medial pterygoid pass through the ganglion without synapsing.
• They supply the tensor veli palatini and tensor tympani muscles.

Functions

• Parasympathetic fibres: They stimulate secretion from the parotid gland.
• Sympathetic fibres: They regulate glandular blood vessels.
• Sensory fibres: They convey general sensation from the parotid gland.
• Motor fibres: They pass through the ganglion to supply tensor veli palatini and tensor tympani.