PAROTID AND INFRATEMPORAL REGIONS

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I. TEMPORAL FOSSA ‑ between superior temporal line (superiorly) and zygomatic arch (inferiorly); contains: Temporalis muscle, Deep Temporal nerves and arteries, branches of Superficial Temporal artery; Auriculotemporal nerve to overlying skin. (Snell Figs. 11‑36, 11-45)

 

II. INFRATEMPORAL FOSSA

 

            A. Boundaries ‑ superior: greater wing of sphenoid and level of the zygomatic arch;.lateral: ramus of mandible; medial: lateral pterygoid plate; anterior: posterior surface of maxillary bone (Atlas Figs. 7.44A,D)

 

            B. Foramina ‑ foramen ovale ‑ for V3 and [Lesser petrosal nerve]; foramen spinosum ‑ for middle meningeal artery and nervous spinosus; mandibular foramen for inferior alveolar nerve, artery, vein; pterygomaxillary fissure ‑ for maxillary artery and branches of maxillary nerve.

 

            C. Contents of Infratemporal Fossa ‑ Medial and Lateral Pterygoid muscles; branches of Mandibular nerve; branches of Maxillary artery; Pterygoid venous plexus. (Snell Fig. 11‑36)    

 

III. MAXILLARY ARTERY ‑ Terminal branch of External Carotid artery

 

            A. Course ‑ Arises posterior to neck of mandible (embedded in parotid gland); course described in three parts: First part posterior and medial to neck of mandible; Second part superficial to or within Lateral Pterygoid muscle; Third part within pterygopalatine fossa. (Atlas Figs. 7.48, 7.47A,B)

 

            B. Branches ‑ branches of first and third parts pass through foramina.

 

First part    

                        1. Deep Auricular A. ‑ through external auditory meatus to outer ear and tympanic membrane

 

                        2. Anterior Tympanic A. ‑ through petrotympanic fissure to middle ear

 

                        3. Middle Meningeal A. ‑ through foramen spinosum to middle cranial fossa and calvarium

 

                        4. (Accessory Meningeal A.) ‑ through foramen ovale to middle cranial fossa and calvarium

 

                        5. Inferior Alveolar A. ‑ through mandibular foramen to lower teeth; gives off mental artery to chin.

 

Second part

                        1. Deep Temporal A. ‑ to temporalis muscle

 

                        2. Pterygoid Arteries ‑ to med. and lat. pterygoids

 

                        3. Masseteric A. ‑ to masseter

 

                        4. Buccal A. ‑ over buccinator muscle to cheek

 

Third part

                        1. Posterior Superior Alveolar A. ‑ through post. superior alveolar foramen to posterior maxillary teeth

 

                        2. Descending Palatine A. ‑ through greater and lesser palatine foramina to hard and soft palate

 

                        3. Artery of Pterygoid Canal ‑ through pterygoid canal to upper pharynx and auditory tube

 

                        4. Sphenopalatine A. ‑ through sphenopalatine foramen to nasal cavity (branch through incisive foramen to palate)

 

                        5. Infraorbital A. ‑ through infraorbital foramen to face (Ant. Sup. Alveolar branches to maxillary teeth)

 

IV. PTERYGOID VENOUS PLEXUS ‑ venae comitantes accompany branches of maxillary artery; have same names; drain to pterygoid venous plexus (superficial to lateral pterygoid muscle); plexus has anastomoses with facial vein and cavernous sinus (by branches following middle meningeal artery); infection can spread from face or teeth to brain.

 

V. TEMPORO‑MANDIBULAR JOINT (TMJ) ‑ synovial joint between head of mandible and mandibular fossa of temporal bone. (Atlas Fig. 7.44A, 8.27; Snell Figs. 11‑39, 11-40)

 

            A. Capsule surrounds joint ‑ is attached tightly to head of mandible, loosely to temporal bone.

 

            B. Articular disc ‑ cartilaginous disc divides joint into two compartments; hinge movements occur in lower compartment; sliding movements in upper compartment.

 

Note: in sliding movements, articular disc moves with head of mandible; disc can get stuck on zygomatic arch and jaw 'locked' open.

 

            C. Ligaments (Atlas Figs. 7.50, 7.51A)

 

                        1. Temporomandibular (Lateral) Ligament ‑ thickening of joint capsule on lateral side; prevents movement posteriorly and inferiorly.

 

                        2. Sphenomandibular Ligament ‑ attached to spine of sphenoid and lingula of mandible; function unclear.

 

                        3. Stylomandibular Ligament ‑ attached to styloid process and posterior border of mandible; function unclear.

 

            D. Movements

 

                        1. Depression‑elevation (opening and closing mouth) ‑ first part hinge movement in lower compartment; second part sliding in upper compartment.                                        

 

                        2. Protrusion‑retrusion (anterior‑posterior) movements ‑ occur as sliding movements in upper compartment.

 

                        3. Lateral movements ‑ sliding movements in upper compartment.

 

 

VI. MUSCLES OF MASTICATION - (Snell Fig. 11-40; Atlas Fig. page 662)

 

MUSCLE

ORIGIN

INSERTION

ACTION

NERVE

Masseter

Zygomatic arch

Mandible - lateral side of ramus

Elevate mandible

V3

Temporalis

Temporal bone

Mandible - coronoid process

Elevate, retrude mandible

V3

Medial

Pterygoid

Lateral pterygoid plate - medial side

Mandible - medial side of ramus

Elevate mandible

V3

Lateral

Pterygoid

1) Sphenoid bone - Greater wing

2) Lateral pterygoid plate - lateral side

1) Mandible - neck

2) Articular disc of TMJ

Depress, protrude mandible

V3

 

Note: Lateral Pterygoid moves articular disc of TMJ anteriorly when opening mouth (Atlas Fig. 7.51A).

 

 

 

 

VII. PAROTID REGION ‑ area between mastoid process and ramus of mandible occupied by parotid gland. (Snell Fig. 11‑35)

 

            A. Development of Parotid gland ‑ develops from buds that arise from ectodermal  lining of primitive mouth; buds branch to form solid cords; cords develop lumens to form ducts; ducts join.

 

            B. Capsule ‑ gland is enclosed in a dense fibrous capsule derived from investing layer of deep cervical fascia; capsule is attached superiorly to zygomatic arch and tympanic part of temporal bone.

 

Note: Mumps is a viral infection that causes swelling of the parotid gland; may be quite painful due to tightness of capsule surrounding parotid.

 

            C. Parotid duct ‑ passes superficial to masseter muscle to pierce buccinator opposite maxillary second molar tooth.

 

Note: Parotid duct makes a 90 degree turn when entering buccinator; this turn acts as a passive valve that prevents air from entering parotid duct when using cheeks to increase pressure in oral cavity, as when blowing a balloon.

 

            D. Surrounding structures

 

                        1. Superficial ‑ Parotid lymph nodes, branches of Great Auricular nerve.

 

                        2. Deep ‑ Posterior belly of Digastric, styloid process and carotid sheath.

 

                        3. Superior ‑ external auditory meatus, TMJ and Auriculotemporal nerve.

 

            E. Structures within parotid (superficial to deep) ‑ Facial nerve and its terminal branches; Retromandibular vein; External Carotid artery and its terminal branches; Auriculotemporal nerve; parotid lymph nodes.

 

Note: When parotid swells during mumps, pain is often referred to ear and temporal region due to compression of Auriculotemporal nerve.

 

            F. Nerve supply ‑ parasympathetic fibers from Glossopharyngeal nerve (otic ganglion).