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Temporomandibular joint Muscles and mechanism of mastication Muscles of facial expression

Temporomandibular joint Muscles and mechanism of mastication Muscles of facial expression. Mark Kozsurek, M.D., Ph.D. mark@kozsurek.hu. EM I., 03/12/2018. Probably you’ve already seen in the dissection room ... Or will see soon. head or condyle of the mandible. coronoid process.

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Temporomandibular joint Muscles and mechanism of mastication Muscles of facial expression

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  1. Temporomandibular jointMuscles and mechanism of masticationMusclesoffacialexpression Mark Kozsurek, M.D., Ph.D. mark@kozsurek.hu EM I., 03/12/2018

  2. Probablyyou’vealreadyseen in thedissectionroom... Orwillseesoon... head or condyle of the mandible coronoid process pterygoid fovea condylar process masseteric tuberosity pterygoid tuberosity

  3. mandibular fossa articular eminence mandibular fossa articular eminence petrotympanic fissure (of Glaser) petrotympanic fissure (of Glaser)

  4. mandibular fossa, articular tubercle Temporomandibularjoint (TMJ) ARTICULAR DISC (made of fibrocartilage) mandibular condyle TMJ consists of two compartments: the discotemporal and discomandibular joints. Note, that instead of hyalin cartilage all the articular surfaces are covered by fibrocartilage!

  5. articular disc is thicker anteriorly and posteriorly • anterior border of the disc is in contact with the upper insertion of the superior belly of the lat. pterygoid muscle • position of the disc is determined by the superior part of lat. pterygoid muscle and the elastic fibres of sup. retrodiscal lamina superior retrodiscal lamina (elastic fibres) inferior retrodiscal lamina (collagen fibres)

  6. AE: articular eminence AB: anterior band IZ: intermediate zone PB: posterior band BZ: bilaminar (retrodiscal) zone C: condyle SLP: sup. part of lat. pterygoid muscle ILP: inf. part of lat. pterygoid muscle Bilaminar (retrodiscal) zone is enclosed by the posterior band of the disc, the superior and inferior retrodiscal laminae and the articular capsule. Is highly vascularised (veinous plexus) and contains a lot of nerve endings.

  7. Capsule, ligaments Capsule is loose, encloses the mandibular fossa and the articular tubercle and inserts around of the neck of mandible. Lateral and medial (temporomandibular) ligaments strenghten the joint capsule and limit anterior and posterior movements. Sphenomandibular ligament is the remnant of the Meckel-cartilage. Just like the stylomandibular ligament has no real function in the movments of the TMJ. Lateral ligament is the strongest and functionally the most important!

  8. Bloodsupply and innervation of TMJ Mainly the articular branches of the auriculotemporal nerve arising from the mandibular division of trigeminal nerve, but branches of the facial nerve contribute to the innervation of the TMJ in approx. 50% of individuals. • from ext. carotid artery: • superficial temporal (st) • from maxillary artery: • anterior tympanic (at) • deep auricular (da) • deep temporal (dt)

  9. Biomechanics of mastication New axis of rotation • Open-closemovement (synonyms: abduction-adductionorelevation-depression) • 1stphase: rotationinthediscomandibularjointaround a bicondylaraxis, e.g. duringtalk; • 2ndphase: glidinginthediscotemporaljointaround a transverseaxisconnectingthetwomandibularforamina.

  10. less then 15° more then 15° Ataround 15° thelateral ligament stretches and avoidsfurtherpurerotationwithinthediscomandibularjoint. Originaltransverseaxisshiftsforward-downward and as a result of movementwithinthediscotemporaljointthehead of themandibleclimbsontothearticulartubercle.

  11. Translation • Condylesmoveforward (protrusion) and backward (retraction) along a sagittal line. Movement is primarilyperformedwithinthediscotemporaljoints. Retraction from the neutral position is almost impossible as the head of mandible is arrested by the external acoustic meatus, and mouth has to be slightly opened for protrusion otherwise upper front teeth will not let the lower ones to move forward.

  12. Grinding • The simpliestdefinition: rotation of themandiblearound an arbitraryverticalaxisperpendiculartotheintercondylar line. The number of suchaxes is unlimited! • Left is the resting, right is the swinging condyle. The left rotates around a vertical axis passing through it, while the right head moves forward and backward. • Right is the resting condyle which performs rotation around a vertical axis, and the left condyle swings anteriorly-posteriorly. • Both the condyles swing: one forward, the other one backward and vice versa. Axis of rotation is a vertical axis located half way between the two condyles.

  13. Muscles of mastication

  14. After removing Temporalis and Masseter muscles

  15. After removing Lateral Pterygoid muscle

  16. Clinical-radiologicalconsiderations

  17. 1. Disc displacement

  18. 2. Bilateral and unilateral (more frequent) dislocation.

  19. Muscles of facialexpression All of them are innervated by the facial nerve (CN7).

  20. Thank you for your attention!

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