Temporal & Infratemporal Fossa PDF

Temporal & Infratemporal Fossa DPM Program Learning Objectives: 1. Describe the boundaries and contents of the infratemporal fossa in terms of: 3.0 a. muscles of mastication (actions and innervations) b. mandibular nerve and its major branches 26 c. chorda tympani (origin and functions) d. major bra...

Temporal & Infratemporal Fossa DPM Program Learning Objectives: 1. Describe the boundaries and contents of the infratemporal fossa in terms of: 3.0 a. muscles of mastication (actions and innervations) b. mandibular nerve and its major branches 26 c. chorda tympani (origin and functions) d. major branches of maxillary artery e. pterygoid plexus of veins 2. Describe the temporomandibular joint (TMJ). 2.0 3. Explain dislocation of the temporomandibular joint. 3.0 4. Describe the major venous anastomoses of the head (e.gs., cavernous sinus, pterygoid plexus, facial veins and veins of the scalp). 3.0 5. Describe the maxillary artery and its major branches. 3.0 1 The Mandible Lateral View of Left Side Medial View of Left Side 2 The temporal fossa is superior to the infratemporal fossa, above the zygomatic arch, and communicates with the infratemporal fossa below through the gap between the zygomatic arch and the more medial surface of the skull. The infratemporal fossa is a wedge-shaped space deep to the masseter muscle and the underlying ramus of the mandible. It communicates with the temporal fossa through the space between the skull and the zygomatic arch. Passing through this communication includes the Temporalis muscle and the deep temporal vessels and nerves. Four muscles of mastication (develop from 1st pharyngeal arch; innervated by mandibular division of trigeminal): 1) Masseter 2) Temporalis 3) Medial pterygoid 4) Lateral pterygoid A chewing or grinding motion occurs when the movements at the temporomandibular joint on one side are coordinated with a reciprocal set of movements at the joint on the other side. Movements of the mandible include depression, elevation, protrusion, and retraction 3 Bondaries of the Infratemporal Fossa Boundaries: Superior (Roof): Greater wing of the sphenoid Inferior: Medial pterygoid muscle Lateral: Medial surface of the ramus of mandible Medial: Lateral pterygoid plate of sphenoid bone Anterior: infratemporal surface of maxilla Posterior: condyloid process of mandible; styloid process of temporal bone 4 Contents of the Infratemporal Fossa Muscles: -Inferior portion of the temporalis muscle -Lateral pterygoid muscle -Medial pterygoid muscle Nerves: -Mandibular division of CNV and its branches -Maxillary n. (a small part) -Chorda tympani nerve (part of facial nerve) Vessels: -Maxillary artery and its branches -Pterygoid venous plexus 5 Muscles of Mastication Temporalis muscle Large fan-shaped muscle that fills the temporal fossa and inserts on the coronoid process of the mandible. -Elevation and retraction of mandible, clenches the teeth -Innervated by mandibular nerve [V3] via deep temporal n. Masseter muscle -Elevation of mandible, clenches the teeth, protracts the mandible -Innervated by mandibular nerve [V3] via masseteric n. 6 Muscles of Mastication Continued Lateral pterygoid -more superficially situated (lateral) O: greater wing of sphenoid bone & lateral pterygoid plate I: neck of the condylar process of mandible -protrusion and side-to side movements of the mandible; depresses mandible -Innervated by mandibular nerve [V3] via lateral pterygoid n. **Both muscles found in the infratemporal fossa. Medial pterygoid O: medial surface of lateral pterygoid plate I:medial surface of the ramus and angle of mandible -Elevation and side-to side movements of the mandible -Innervated by mandibular nerve [V3] via medial pterygoid n. 7 Maxillary Artery Larger of the two terminal branches of the EXTERNAL CAROTID ARTERY, the other being the superficial temporal artery. From its origin, the maxillary artery passes anteriorly, deep to the neck of the mandible. It then courses through the infratemporal fossa passing superficial or deep to the Lateral Pterygoid muscle and leaves the infratemporal fossa by entering the pterygopalatine fossa through the pterygomaxillary fissure. For descriptive purposes the maxillary artery is divided into three parts: First part: (deep to ramus of mandible) Branches include: Middle meningeal a. –supplies the dura mater Inferior alveolar a. –mandible bone, mandibular teeth (descends along the lateral pterygoid muscle, enters mandibular foramen, terminates as mental aa. after it travels through the mental foramen) Second part: (either superficial or deep to the Lateral Pterygoid muscle) Branches include: Pterygoid branches Masseteric a.-masseter m. Buccal a.-the cheek and buccinator mm. Third part: (passes through the pterygomaxillary fissure into the pterygopalatine fossa) Branches include: Infraorbital a.-sensation of the skin of cheek, upper lip, lateral nose 8 9 Pterygoid Plexus The pterygoid plexus of veins is found between the two pterygoid muscles and between the lateral pterygoid and the temporalis. Receives tributaries which correspond to the branches of the maxillary artery. Consequently, it receives drainage from: the Paranasal Sinuses; the Oral Cavity; structures of the Infratemporal Fossa In addition, it communicates with the CAVERNOUS SINUS by emissary veins as well as a large, direct communication with the facial vein called the deep facial vein. The pterygoid plexus drains into the maxillary vein. 10 Mandibular Nerve and its Branches The third division of the Trigeminal Nerve, the mandibular division is composed of a sensory root and a motor root. The sensory root arises from the TRIGEMINAL GANGLION while the motor root arises from the brain stem (i.e., pons). The two roots exit the cranial cavity via the FORAMEN OVALE where they form a common trunk (i.e., the mandibular division) and enter the infratemporal fossa. Shortly after exiting from the foramen ovale, the common trunk divides into an anterior division (which is primary motor) and a posterior division (which is largely sensory). Prior to dividing, however, the trunk gives rise to two branches (Meningeal branch and Nerve to Medial Pterygoid). Branches of the trunk: 1) Meningeal branch: re-enters cranial vault through foramen spinosum; sensory innervation to the dura mater 2) Nerve to medial pterygoid muscle: efferent to medial ptyergoid and branches to tensor veli palatini m. & tensor tympani muscle Branches of Anterior Division (largely motor) and Posterior Division (largely sensory) found on following slides. 11 Branches of the Anterior Division of Mandibular Nerve Anterior Division (largely motor) includes: Masseteric nerve: supplies masseter Deep temporal nerve: supplies temporalis m. Nerve to lateral pterygoid m.: supplies lateral pterygoid m. Buccal nerve: exclusively sensory supplying the skin and mucous membrane of the cheek (not to be confused with buccal from facial nerve which is purely motor) 12 Branches of the Posterior Division of Mandibular Nerve Posterior Division (largely sensory) includes: Auriculotemporal nerve: supplies sensory innervation to skin of the temporal region and anterior ear (also carries postgang. Parasympathetic fibers from the otic ganglion to the parotid gland) Lingual nerve: general sensation to the anterior two-thirds of the tongue Inferior alveolar nerve: enters the mandibular foramen posterior to the lingual, leaves via mental foramen to supply skin of the chin 13 The Chorda Tympani Nerve Recall that intracranially, the FACIAL NERVE has a portion known as the NERVUS INTERMEDIUS. The nervus intermedius contains fibers which convey taste (i.e., SVA [VA] from the anterior twothirds of the tongue (with the exception of those found in the vallate papillae) and parasympathetic innervation (i.e., GVE [VE] to the submandibular ganglion (located within the submandibular triangle). To be discussed further in oral cavity lecture. The SVA and GVE fibers form the CHORDA TYMPANI BRANCH OF THE FACIAL NERVE. This nerve leaves the petrous portion of the temporal lobe through the petrotympanic fissure (a slit-like opening posterior to the mandibular fossa) to enter the infratemporal fossa and join the lingual branch of V3. NOTE: The fibers of the chorda tympani are then conducted by the lingual nerve to the tongue for its taste distribution (please keep in mind that difference between taste sensation carried by the chorda tympani, and general sensation as carried bythe lingual nerve fibers) and into the submandibular ganglion for its parasympathetic distribution 14 Temporomandibular Joint The temporomandibular joint is a synovial (i.e., a diarthrosis) joint by which the head of the mandible (inferiorly) articulates with the mandibular fossa and articular eminence of the temporal bone (superiorly). It is a rather simple articulation. It differs from many other joints, however, in that the joint cavity is divided essentially into two compartments: 1) Superior gliding (allows for protrusion and retraction of the mandible) 15 2) Inferior hinge compartment (allows for hinge-like depression and elevation of the mandible Ligaments of the Temporomandibular Joint Three extracapsular ligaments are associated with the temporomandibular joint—the lateral, sphenomandibular, and the stylomandibular ligaments: 1.The lateral ligament is closest to the joint, just lateral to the capsule, and runs diagonally backward from the margin of the articular tubercle to the neck of the mandible. 2.The sphenomandibular ligament is medial to the temporomandibular joint, runs from the spine of the sphenoid bone at the base of the skull to the lingula on the medial side of the ramus of the mandible. 3.The stylomandibular ligament passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible. 16 Temporomandibular Joint Dislocation The TMJ is the only joint that can be dislocated without the action of any external force. For example, subluxation may occur: -during yawning -taking a large bite -extraction of teeth -blow to the chin when mouth is open (laughing, gaping, yawning) The dislocation is usually anterior and almost always bilateral. Dislocation occurs when the head of the mandible passes anterior to the articular eminence into the infratemporal fossa. The mandible becomes fixed in the open position when dislocated. Reduction is accomplished by first manually 17 depressing the angle of the mandible and then elevating the chin and pressing it posteriorly.