Anatomy: Parotid Region

• The parotid region is located in the face
• The head can be divided into regions for communication about structure locations, injuries, and pathologies
• The facial region includes the orbital, infra-orbital, buccal, parotid, zygomatic, nasal, oral, and mental regions

Parotid Region Borders

• The posterolateral facial region is bounded superiorly by the zygomatic arch
• It is bounded inferiorly by the angle and the inferior border of the mandible
• The ramus of the mandible bounds it medially
• The anterior border of the masseter muscle bounds it anteriorly
• The external ear and anterior border of the sternocleidomastoid muscle bounds it posteriorly

Parotid Region Contents

• The region contains the parotid gland and duct
• The parotid plexus of the CN VII (facial nerve) is located here
• The retromandibular vein resides in this area
• The external carotid artery is in the parotid region
• The masseter muscle is located in the parotid region
• Parotid lymph nodes are on the parotid sheath and within the gland
• The five terminal branches of the facial nerve exit via the anterior border of the gland
• The branching pattern forms a radiating pattern from the anterior border which is known as "pes anserinus"

Parotid Gland

• The parotid gland is the biggest of the 3 paired salivary glands
• It is made up mostly of serous acini
• The gland is enclosed by the parotid sheath which is a firm and unyielding capsule from the deep cervical fascia
• It lies in a deep hallow under the external auditory meatus
• It lays behind the ramus of the mandible
• The gland sits in front of the sternocleidomastoid muscle
• The parotid gland has an irregular shape
• The apex sits posterior to the the angle of the mandible
• The base is related to the zygomatic arch
• The subcutaneous lateral surface is almost flat
• The facial nerve splits the gland into superficial and deep lobes
• Fatty tissue between the lobes gives flexibility for motion of the mandible

Parotid Duct

• The parotid (Stensen's) duct passes horizontally from the anterior edge of the gland
• It passes forward over the lateral masseter muscle, about one fingerbreadth inferior to the zygomatic arch
• The duct turns medially, deep into the buccal fat pad, and piercing the buccinator muscle
• The duct enters the oral cavity vestibule via a small orifice (papilla) opposite the 2nd maxillary molar tooth
• The duct's pathway in the buccinator muscle works like a valve, and keeps the duct from inflating during blowing
• It is about 2 inches (5 cm) long
• It is represented by the middle 1/3rd of a line extending from

Vascular Supply of the Parotid Gland

• The arterial supply comes from the external carotid artery and terminal branches
• The venous drainage occurs via the retro-mandibular vein
• Lymph drainage goes into parotid and then deep cervical lymph nodes

Innervation of Parotid Gland and Related Structures

• The auriculotemporal and great auricular nerves give sensory fibers to the gland
• These nerves innervate the sheath, and the skin above
• The parasympathetic components of the glossopharyngeal nerve (CN IX) supplies presynaptic secretory fibers to the otic ganglion
• Postsynaptic parasympathetic fibers are sent from the ganglion to the gland by the auriculotemporal nerve
• When stimulated, produces a thin, watery saliva
• Sympathetic fibers come from cervical ganglia via the external carotid nerve plexus on the external carotid artery

Buccal Fat Pad

• The buccal fat pad enables chewing and suckling, mostly in infants
• Gliding pads help the mastication muscles move
• It acts as a cushion, which protects sensitive facial muscles from injuries due to the muscles or exterior forces
• Blood supply arrives from buccal and deep temporal (maxillary artery), transverse facial (superficial temporal artery), and facial arteries
• Cheeks get innervation from buccal branches of the mandibular nerve

Clinical Notes on Parotid Region

• Parotid duct injury can occur from facial injuries or inadvertent surgical cuts
• The parotid gland is essentially superficial and deep, with the facial nerve running in between
• Benign parotid neoplasms rarely cause face palsy
• A malignant parotid tumor can cause unilateral facial paralysis

Parotid Gland Infections

• The parotid gland may become inflamed from retrograde bacterial infection from the mouth via the parotid duct
• Infection can also come via the bloodstream, as in mumps
• In both scenarios, the gland is swollen; it is painful when swollen due to the strong fascial capsule which is derived from investing layer of deep cervical fascia, and limits swelling

Frey's Syndrome

• Frey's syndrome results from damage to the auriculotemporal and great auricular nerves
• When healing from damage to these nerves, parasympathetic secretomotor fibers of the auriculotemporal nerve connects the distal end of the great auricular nerve
• Eventually, the cutaneous sympathetic nerves which control sweat glands connect to the healing nerves, meant for saliva production

Temporal and Infratemporal Region

• The lateral side of the skull has two parts which are divided by the zygomatic arch
• These parts are; The temporal fossa and infratemporal fossa

Temporal Fossa Boundaries

• Inferiorly, it is bound by the zygomatic arch and is continuous with infratemporal fossa deep to zygomatic arch
• Superiorly and posteriorly, it is bound by temporal lines
• Anteriorly, it is bound by the posterior surface of the frontal and zygomatic processes of the frontal and zygomatic bones

Floor of the Temporal Fossa

• The floor is formed by the frontal and parietal bones superiorly
• and the greater wing of the sphenoid and squamous temporal inferiorly
• At the pterion, the frontal, parietal, sphenoid, and temporal bones meet at an H-shaped sutural junction
• The pterion is important because it overlays the anterior branch of the middle meningeal artery
• Its location overlays the lateral fissure of the cerebral hemisphere
• It corresponds to the location of the anterolateral (sphenoidal) fontanelle on a neonatal skull, closing 3 months after birth
• Superior temporal line gives attachment to the temporal fascia
• Inferior temporal line provides

Temporal Fossa Contents

• Temporalis muscle
• Zygomaticotemporal nerves
• Deep temporal nerves
• Deep temporal artery

Temporalis Muscle

• Temporalis muscle is fan shaped, filling much of the temporal fossa
• From the body surfaces of the temporal fossa and temporal fascia, it originates
• It inserts on coronoid process of the mandible
• Anterior fibers are oriented vertically, and its posterior fibers oriented horizontally
• The temporalis is a powerful elevator of the mandible
• Its posterior fibers retract the mandible, enabling chewing
• Deep temporal branches of the mandibular nerve are responsible for its nerve supply
• Deep temporal arteries provide blood supply

Infratemporal Fossa

• The infratemporal fossa is irregularly-shaped
• It is inferior and medial to the zygomatic arch
• Located between the ramus of the mandible and the pharynx
• Contents include medial and lateral pterygoid muscles
• Maxillary artery resides there
• Pterygoid venous plexus also
• The mandibular nerve runs through
• Contains chorda tympani nerve and otic ganglion

Infratemporal Fossa Boundaries

• Anteriorly, the posterior (infratemporal) surface of the maxilla serves
• Posteriorly, the mandibular fossa, styloid process & spine of the sphenoid
• The infratemporal crest superiorly
• Inferiorly: Alveolar border of the maxilla
• Medially, its bound by the lateral pterygoid plate
• Laterally, it is bound by the zygomatic arch and ramus of mandible

Infratemporal Fossa Communications

• Connection to the temporal fossa via the zygomatic arch
• Communication with the cranial cavity via the foramen ovale and foramen spinosum
• Communication with the tympanic cavity via the petrotympanic fissure
• Connects to Maxillary teeth and sinus through the posterior superior alveolar foramina
• Connects to the Orbit by way of the inferior orbital fissure
• The infratemporal fossa Connects to the pterygopalatine fossa via the pteryomaxillary fissure
• It Connects to the Submandibular region deep to the mandible

Pterygopalatine Fossa

• The pterygopalatine fossa is small and pyramidal-shaped.
• Located in the deep lateral aspect of head, inferior and posterior to the orbit
• Contains the terminal branches of the maxillary artery
• Carries maxillary nerve, nerve of the pterygoid canal, and the pterygopalatine ganglion

Boundaries of Pterygopalatine Fossa

• Anterior by way of the posterior (infratemporal) surface of the maxilla
• Posteriorly by way of the base of pterygoid process
• Inferiorly by way of the inferior margin of pteryomaxillary fissure
• Medially by way of the posterolateral wall of the nasal cavity, perpendicular plate of the palatine bone
• Laterally by way of the pteryomaxillary fissure

Primary communications of Pterygopalatine Fossa

• Infratemporal fossa via pteryomaxillary fissure
• Cranial cavity through foramen rotundum, and pterygoid canal
• Connects to nasal pharynx through pharyngeal canal
• It Connects to the Orbit by way of the inferior orbital fissure
• Its connected to Maxillary teeth and sinus through the infraorbital canal
• Communication with nasal cavity through the sphenopalatine foramen

Arteries of Head & Neck

• External carotid artery splits into the superficial temporal and maxillary arteries at about the neck of the mandible
• Superficial temporal is smaller, and ascends into temporal fossa
• Smaller, and runs upward into temporal fossa

Maxillary Artery

• The maxillary artery, larger, ascends across infratemporal fossa and then deep and through pteryomaxillary fissure and into the pterygopalatine fossa

Branching of Superficial Temporal Artery

• Transverse facial artery
• Anterior (frontal) branch
• Posterior (parietal) branch

Branching of Maxillary Artery

• Small branches to the external auditory meatus and tympanic membrane
• Middle meningeal artery
• Inferior alveolar artery
• Muscular branches to the muscles of mastication
• Posterior superior alveolar artery
• Descending palatine artery
• Pharyngeal branch
• Artery of pterygoid canal
• Infraorbital artery
• Sphenopalatine artery

Nerves of Head & Neck

• The maxillary nerve, a division of the trigeminal nerve, enters the cranium via foramen rotundum and enters the pteryopalatine fossa
• It sends sensory branches across a broad range of the cranium, midface, nasal cavity, oral cavity, and the nasopharynx

Mandibular Nerve

• The mandibular nerve, another division of the trigeminal, goes through the foramen ovale and into deep upper aspect of the infratemporal fossa
• Divides immediately, sending many motor/sensory branches into the cranium and the infratemporal and temporal fossae
• Also innervates the lower jaw, oral cavity, and lower face

Branches of Maxillary Nerve

• Middle meningeal nerve
• Ganglionic branches to the pterygopalatine ganglion
• Zygomatic nerve
• Posterior superior alveolar nerve
• Infraorbital nerve
• Greater and lesser palatine nerves
• Nasopalatine nerve
• Pharyngeal nerve

Branches of Mandibular Nerve

• Meningeal (spinous) nerve
• Motor branches to the muscles of mastication
• Tensor veli palatini
• Tensor tympani
• Buccal nerve
• Lingual nerve
• Inferior alveolar nerve
• Auriculotemporal nerve

Branches of Pterygoid Canal Nerve

• Nerve of the pterygoid canal is a composite of the greater petrosal (parasympathetic branch of facial nerve) and the deep petrosal nerve (sympathetic) coming from the carotid plexus
• The combined nerves join the pterygopalatine ganglion.
• Distributes postganglionic fibers along maxillary nerve branches.
• -Lesser petrosal nerve' is a parasympathetic component of the glossopharyngeal nerv
• It extends from mid ear into infratemporal fossa before joining the otic ganglion
• Postgang fibers then join the auriculotemporal branch of the mandibular nerv

Muscles of Mastication

• The muscles of mastication move the mandible and act on the tempromandibular joint
• There are 4 muscles listed in mastication:
  • Temporalis muscle
  • Masseter muscle
  • Medial pterygoid muscle
  • Lateral pterygoid muscle
• The medial pterygoid muscle has deep and superficial head

Masseter Muscle

• The masseter muscle originates from the lower and medial border of the zygomatic arch
• The masseter inserts on the lateral surface on the ramus of the mandible
• The muscles action is elevation of the mandible
• Innervated by the nerve to masseter from the anterior division of the mandibular nerve

Medial Pterygoid Muscle

Origin

• Deep head from the medial surface of the lateral pterygoid plate
• Superficial head from the tuberosity of the maxilla Insertion
• Inserted to the roughened medial surface of the ramus of mandible near the angle Action
• It elevates the mandible and protrudes the lower jaw Nerve supply
• Its by the nerve to medial pterygoid from the mandibular nerve

Lateral Pterygoid Muscle

• The lateral pterygoid has two heads: upper and lower heads
• The upper head origin occurs from the infratemporal surface of the greater wing of sphenoid
• Lower head origin comes about from lateral surface of the lateral pterygoid plate

Insertion

• Inserts into the pterygoid fovea of the neck and articular disc of the temporomandibular joint. Action
• Open mouth by pulling forward mandible onto the articular tubercle
• It is the major protruder of the lower jaw. Nerve supply by nerve to lateral pterygoid by mandibular nerve

Temporomandibular Joint (TMJ)

• The articular tubercle and the anterior portion of the mandibular fossa reside above
• The head (condyloid process) is below
• Articular surfaces have fibrocartilage
• TMJ is synovial.
• Articular disc: The disc divides it into upper and lower cavities

TMJ Capsule

• Surrounds joint
• Attached above to the articular tubercle and the margins
• Below TMJ is the neck of the mandible.

TMJ Synovial Membrane

• Lines the capsule in the upper and lower cavities of these joints Nerve supply
• Auriculotemporal, masseteric branches of mandibular nerve. Its divided the joint into the upper and the lower

The disc is attached circumferentially to the capsule and the tendon of the lateral pterygoid muscle

• Moves with head as when protraction + retraction of mandible.
• ( upper is concave/convex (backwards) + lowe surface is concave

Ligaments of Joints

• Lateral temporomandibular ligament run back and down from tubercle
• Sphenomandibular ligament lies inside
• Its attached above to the spine of bone-below lingula: mandibular foramen
• Stylo: band that from apex of process and down goes down from/to angle

Movements of Mandible

• It can go up or come down, protrude out, or return inward
• It can also move in rotation

Mandible Depression

• It is opened as on axis, disc turns on surface
• Made about a with two muscle contraction of digastrics, geniohyoids, and mylohyoids and with these lateral pterygoids

Mandible Elevation

• Initial step is jaw and head move on disk surface by contraction
• Pulled/ the jaw moves up by posterior.

TMJ: protrusion

• The joint: disc moves forward & over ridge. with movement
• With both contracted teeth move down (by medial of the joints )

TMJ: Retraction

• The joint: disk moves back, by - posterior is by (fibrosis) movement sides , by rotation which goes in by work/harmony

TMJ Relations

• Its: Jaw- lower sides/nerves- arteries
• The Posteriorly tympanic plate and the foramen, sides
• At The (the space) + (nerve space for that with ear)
• Superiorly The sides. (nerve)

TMJ Clinical Significance

• Lateral is front from meatus . Lateral's strong point prevents the head from the jaw. From ( fractures/back and of these the jaw)

• If the surface gets torn then with get clicks

TMJ Dislocation

• In TMJ the bone is goes down, on bone.
• Disc for move/touch the tubercle
• Can move too
• In it bone be ( contraction ): can move ridge/disc from
• Sides: then be on top sides-heads ( of these be (bone),