If the parotid bed was a crossroads,
then the deep face is something far more powerful:
It is an engine room.
Hidden beneath the mandible and zygomatic arch,
this is where:
Force is generated
Motion is refined
Rhythm becomes automatic
Not visible.
But essential.
Because here, the face stops expressing…
and starts working.
PART I - DEFINING THE DEEP FACE
The deep face lies:
Deep to the mandible
Beneath the zygomatic arch
Extending into the temporal and infratemporal fossae
It houses:
3 of the 4 muscles of mastication (masseter sits superficial)
Major neurovascular structures
The functional core of the stomatognathic system
This is not surface anatomy.
This is operational anatomy.
PART II - THE SPACES: WHERE EVERYTHING HAPPENS
1. Temporal Fossa - The Power Fan
Located above the zygomatic arch (the “temple”):
Bounded by temporal lines
Floor formed by frontal, parietal, temporal, and sphenoid bones
The diagram on page 190 (Fig 12-1) shows this as a broad, shallow basin.
Inside it sits the temporalis muscle - fan-shaped, spreading wide.
A reservoir of force, gathered before being delivered.
2. Infratemporal Fossa - The Deep Chamber
Located:
Inferior to zygomatic arch
Deep to mandible
An irregular, open space with no true inferior boundary.
The diagram on page 190–191 (Fig 12-2 & Table 12-1) shows:
Contents:
Muscles of mastication (except masseter)
Maxillary artery
Pterygoid venous plexus
Mandibular nerve (V3)
Communications:
Cranial cavity (foramen ovale, spinosum)
Orbit (inferior orbital fissure)
Pterygopalatine fossa
Neck spaces
This is not a compartment.
It is a gateway system.
PART III - THE MUSCLES: ARCHITECTS OF FORCE
There are four muscles of mastication:
1. Masseter - The Power Clamp
Origin: Zygomatic arch
Insertion: Lateral mandible
Function: Strong elevation (closing jaw)
2. Temporalis - The Precision Elevator
Fan-shaped
Inserts onto coronoid process
Functions:
Elevation
Retraction (posterior fibres)
3. Medial Pterygoid - The Mirror Muscle
Mirrors masseter on inner side
Forms pterygomasseteric sling
Function:
Elevation of mandible
Like two hands holding the jaw from both sides.
4. Lateral Pterygoid - The Initiator
Two heads:
Superior: stabilises TMJ
Inferior: opens jaw + protrusion
This is the only muscle that truly starts opening.
Functional Summary
Elevators: Masseter, temporalis, medial pterygoid
Depressor: Lateral pterygoid
Side-to-side: Coordinated pterygoids
PART IV - FASCIA: THE CONTAINMENT SYSTEM
The muscles are wrapped within a masticator compartment:
Formed by deep fascia
Encloses:
Muscles
Mandibular ramus
Neurovascular structures
The diagram on page 194 (Fig 12-3) shows this compartment clearly.
Not just structure -
containment, continuity, and potential spread.
PART V - THE VASCULAR ENGINE
Maxillary Artery - The Lifeline
A terminal branch of external carotid:
Passes deep to mandible
Travels through deep face
Divided into 3 parts:
Mandibular
Pterygoid
Pterygopalatine
The diagram on page 203 (Fig 12-9) shows its branching complexity.
Supplies:
Muscles of mastication
Teeth
TMJ
Nasal and oral structures
It feeds the engine.
Venous System - The Hidden Risk
Pterygoid venous plexus:
Large interconnected network
Communicates with:
Face
Orbit
Cavernous sinus
The diagram on page 204 (Fig 12-10) shows this dangerous connectivity.
This is where infection travels… silently.
PART VI - INNERVATION: THE CONTROL SYSTEM
Trigeminal Nerve (CN V)
Three divisions:
V1 (ophthalmic)
V2 (maxillary)
V3 (mandibular)
Mandibular Division (V3) - The Key Player
Only division with motor + sensory
Exits via foramen ovale
Divides into:
Anterior (motor dominant)
Posterior (sensory dominant)
Motor Supply
Muscles of mastication
Mylohyoid
Anterior belly of digastric
Sensory Supply
Teeth
TMJ
Lower face
Anterior 2/3 of tongue (general sensation)
PART VII - MASTICATION: THE ORCHESTRATED MOVEMENT
Mastication is:
Initially conscious
Then becomes automatic rhythm
Sequence:
Food enters
Positioned by tongue and cheek
Crushed by molars
Jaw moves:
Up/down
Side-to-side
Forward/back
Controlled by:
CNS circuits
Proprioceptors in periodontal ligament
A learned rhythm that becomes instinct.
PART VIII - CLINICAL THREADS
1. Masticator Space Infection
Spreads rapidly via fascial planes
Patients very unwell
Requires urgent care
2. Anaesthetic Complications
Needle may puncture pterygoid plexus
→ Haematoma
→ Possible spread to cavernous sinus
3. Mandibular Nerve Injury
Jaw deviates
Loss of sensation:
Chin
Teeth
Tongue (anterior 2/3)
4. Temporomandibular Disorder (TMD)
Pain, clicking, limited movement
Multifactorial causes:
Stress
Trauma
Malocclusion
Key Takeaways
The deep face is the functional core of mastication
Temporal and infratemporal fossae define its spaces
Muscles of mastication generate complex jaw movements
Maxillary artery supplies the region; pterygoid plexus poses risk
Mandibular nerve (V3) provides motor and sensory control
Mastication is a coordinated, semi-automatic process
