Infratemporal and temporal region l human anatomy revision for dental students

Infratemporal and temporal region l General head and neck anatomy revision for dental students

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The infratemporal fossa

Site:

• situated beneath the base of the skull, between the side wall of the pharynx and the ramus of the mandible
• N.B.: It’s also refered to as the parapharyngeal or lateral pharyngeal space.

 

Boundaries:

• Anteriorly: the posterior surface of maxilla.
• Posteriorly: the styloid & mastoid process
• Medially: the lateral pterygoid plate
• Laterally: ramus if mandible and its coronoid process
• Above: infratemporal surface of the greater wing of sphenoid bone “perforated by the foramen ovale and foramen spinosam”

 

Communications:

1. Communicates with the temporal fossa deep to zygomatic process
2. Communicates with the orbit through the inferior orbit al fissure.
3. Communicates with the pterygopalatine fossa through the pterygomaxillary fissure
4. Communicates with the middle cranial fossa through the foramen ovale and foramen spinosum

 

Contents:

1. Deep part of parotid gland
2. The medial pterygoid muscle
3. The lateral pterygoid muscle
4. The insertion of temporalis into the cronoid process
5. The mandibular nerve and its branches together with the otic ganglion
6. The chorda tympani
7. The maxillary artery and its branches
8. The pterygoid venous plexus
9. The posterior superior alveolar branches of maxillary nerve

Muscles of mastication.

1.   Masseter:      

• Origin:       Lower border & inner surface of zygomatic arch.
• Insertion:   outer surface of the ramus of the mandible.
• Nerve supply : Nerve to masseter (from anterior division of mandibular nerve).
• Action :    

1. Elevation of the mandible.       
2. Antigravity muscle.
3. Protraction (superficial head). 

2.   Temporalis:

• Origin: boney floor of temporal fossa and the deep surface of overlying temporal fascia
• Insertion: its tendon passes deep to zygomatic arch and inserted into anterior border of coronoid process medially and anterior border of ramus.
• Nerve supply: deep temporal nerves branches of anterior division of the mandibular nerve
• Action: anterior and superior fibers elevate the mandible , Posterior fibers retract the mandible

 

3.   Lateral pterygoid muscle:

• Origin: 2 heads, Upper head rises from the infratemporal surface of greater wing of sphenoid , Lower head rises from the lateral surface of the lateral pterygoid plate..
• Insertion: from of neck of mandible and the articular disc of TMJ.
• Nerve supply: anterior division of mandibular nerve
• Action: pulls the neck of the mandible anteriorly . (side to side as in chewing movements)

 

4.   Medial pterygoid muscle:

• Origin: 2 heads, Superficial head rises from tuberosity of maxilla , Deep head from medial surface of lateral pterygoid plate
• Insertion: medial surface of the angle of the mandible
• Nerve supply: mandibular nerve (main trunk)
• Action: elevates the mandible side to side (chewing) movement

Maxillary artery

Origin:

• arises within the substance of parotid gland, deep to neck of mandible as the larger terminal branch of external carotid artery (ECR).

Course & relations: the course of the artery is divided into 3parts:

1. First part: Runs forwards within the parotid gland between the neck of mandible and sphinomandibular ligament along the lower border of posterior part of lateral pterygoid muscle.
2. Second part:  Runs upwards & forwards along the lateral surface of lower head of lat. Pterygoid muscle.
3. Third part: (pterygopalatine art.) : Dips between two heads of lateral pterygoid muscle then passes through the pterygomaxillary fissure to reach the pterygopalatine fossa.

 

Termination:

• Ends by becoming the infra-orbital artery That enters the orbit through inf. Orbital fissure then runs along the floor of the orbit in the infraorbital groove then infraorbital canal accompanied by the infra-orbital nerve (continuation of maxillary nerve)  , The infraorbital artery Finally reaches the face through the infraorbital foramen

 

Branches from the 1^st part: (M.I.A.D.A)

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

Branches from the 2^nd part:

• Gives 5 muscular branches supplying the four muscles of mastication & the 5h one supplies the buccinators m.

Branches from the 3^rd part (pterygoid artery)

• Posterior Superior Alveolar (dental) artery With the inferior ophthalmic vein via a communicating vein passing through inferior orbital fissure.
• Clinical importance: Infection in the dangerous area of the face may reach the pterygoid plexus of VV. Then it can pass to the cranial cavity via emissary veins causing cavernous sinus thrombosis.

 

Mandibular division of the trigeminal nerve

• The sensory and motor roots of the mandibular division emerge from the skull through the foramen ovale, where the two roots join and appear as the mandibular nerve
• The nerve then descends between the tensor velli palatine medially and the lateral pterygoid laterally &
• Divides into a small anterior & posterior division

 

Branches from the main trunk

1. A meningeal branch
2. The nerve to medial pterygoid

 

Branches from the anterior division:

• It’s the smaller division and it’s motor, except for one branch ( the buccal nerve)

1. The masseteric nerve
2. The two deep temporal nerves
3. The nerve to lateral pterygoid
4. The buccal nerve

 

Branches from the posterior division

• It’s the larger division & it’s sensory except for the motor fibers that are distributed via the mylohypid nerve in the inferior alveolar nerve.

1. The auricotemporal nerve
2. The lingual nerve
3. The inferior alveolar nerve, that is made up of motor (mylohyoid n.) & sensory nerve fibers
4. 2-3 lesser palatine artery .
5. Greater palatine a.
6. Sphenopalatine artery
7. Pharyngeal artery
8. Artery of pterygoid canal

• Site: It’s a network of veins lying around & inside substance of lat. Pterygoid m.
• Formation: formed by veins accompanying the branches
• Drainage: drained Posteriorly by the maxillary v. that is  inside the substance of parotid gland by uniting with the superficial temporal v. to form retromandibular vein.
• Communications:

1. With the ant. Facial v. through the deep facial vein that passes deep to ramus of mandible
2. With the cavernous sinus via valveless emissary veins passing through the foramen ovale or the foramen lacerum

Pterygopalatine fossa

• It’s a small space below & behind the apex of the orbital cavity and medial to the pterygomaxillary fissure.
• Its shape: an inverted pyramid

 

Boundaries:

 

1. Anterior wall:  Post. Surface of maxilla
2. Posterior wall: Pterygoid process of sphenoid bone
3. Medial wall: Perpendicular plate of palatine bone that forms part of the lat. Wall of the nasal cavity

Communications:

1. Communicates laterally with the infratemporal fossa through pterygomaxillary fissure
2. Communicates medially with the nasal cavity through the sphenopalatine foramen
3. Communicates superiorly with he middle cranial fossa through foramen rotundum
4. Communicates anteriorly with the orbit through the inferior orbital fissure
5. Communicates inferiorly with the palate through the greater & lesser palatine canals.

 

Contents:

• The terminal part of maxillary artery( pterygopalatine artery)
• The maxillary nerve
• Sphenopalatine ganglion suspended from the nerve

 

The maxillary nerve:

It leaves the middle cranial fossa through the foramen rotundum, to enter the pterygopalatine fossa.

• It crosses the upper part of the fossa and enters the orbit by passing through the inferior orbital fissure; here it’s called the infraorbital nerve.
• The infraorbital nerve runs forward on the floor of the orbit, first in the infraorbital groove and then in the infraorbital canal.
• It appears on the face by emerging through the infraorbital foramen
• Branches:

1. A meningeal branch
2. The ganglionic branches are two short nerves that hold up the pterygopalatine ganglia.
3. Posterior superior alveolar nerve
4. Zygomatic nerve
5. Middle superior alveolar nerve
6. Anterior superior alveolar nerve

 

Sphenopalatine ganglion:

• Deeply placed in pterygopalatine fossa.
• Gives parasympathetic secretomotor for lacrimal gland
• It has 5 branches that are distributed to the nose, palate & nasopharynx. Each branch carries a mixture of: sensory, secretomotor & sympathetic fibers.
• It’s known as the ganglion of hay fever

Temporal fossa

Site:

• situated on the side of the head

Boundaries:

1. Above and behind : The superior  Temporal line
2. Below : The zygomatic arch
3. Anteriorly  : The frontal process of zygomatic

 

• Its roof (lateral wall) : Temporalis fascia
• Its floor (medial wall) : The part of the side of the skull that includes the pterion, where the frontal, the parietal and squamous part of temporal bone articulate with the greater wing of sphenoid (roughly H shaped area)

its clinical importance

• The fossa is filled by the “temporalis muscle” that arises from the bony floor and from the deep surface of overlying temporal fascia
• The fossa communicates with the infratemporal fossa deep to the zygomatic arch ( at the level of infratemporal crest of greater wing of sphenoid).

                                               

Contents:

1. The temporalis muscle & its covering fascia
2. Deep temporal nerves à 2 in number arising from the anterior division of the mandibular n. à leave infratemporal fossa to enter the deep surface of temporalis muscle to supply it.
3. Deep temporal arteries, also 2 in number, are branches of the maxillary artery accompany the nerves and supply the temporalis muscle.
4. Auricotemporal nerve à branch of the posterior division of mandibular nerve à emerges from the upper border of parotid gland behind T.M.J à crosses root of zygomatic arch in front of auricle & behind superficial temporal artery.
5. Superficial temporal artery:

• The smaller terminal branch of ECA ( Ext. Carotid Artery)
• Emerges from the upper border of parotid gland behind T.M.J
• Crosses the root of zygomatic arch in front of Auricotemporal nerve & auricle, here its pulsations can be easily felt.
• Ascends onto the scalp and divides into ant. & posterior divisions