hnL3 - temporomandibular joint (TMJ)

• discuss the anatomy of the temporomandibular joint (TMJ):

  • the joint between the temporal bone and the condylar head of the mandible, which has two articulations (location where two or more bones meet and join), one on each side of the head.
  • these allow mandibular movements in speech and mastication (process of chewing food).
  • articular eminence [slope] = the bone on which the condylar process slides during mandibular movements.
  • glenoid fossa [cup-shaped] = contributes to the formation of the temporomandibular joint.
  • post glenoid process [projection] = a bony prominence.
• discuss the joint classification of the temporomandibular joint (TMJ):

  synovial joint:

  • capsule of the joint attached below the fibrocartilage on each articular surface, and encloses the joint.
  • capsule of the joint is covered internally by a synovial membrane, which secretes synovial fluid into the joint cavity, to lubricate the joint = smooth movement and reduced friction.
  • TMJ also has an intra-articular disc of fibrocartilage between the opposing articular surfaces.
• discuss the action of the temporomandibular joint (TMJ)- opening the mouth:

  stage 1:

  • initial hinge movement does not involve anterior displacement of the condyle.
  • passive movement - no muscular contraction
  • creates the freeway space at rest.

  stage 2 (active opening):

  • muscular contraction
  • condyle displaced onto the articular eminence by lateral pterygoid - condyle and disc pulled forward.
  • mandible then pulled down and back by digastric (one of the accessory muscles of mastication - rotation.
  • point of rotation is the lingula, not the head of the condyle.
• discuss the action of the temporomandibular joint (TMJ) - closing the mouth:

  stage 1:

  • elevation of the mandible by contracting the masseter (superficial belly), temporalis (vertical fibres), and medial pterygoid.

  stage 2:

  • retraction of the condyles to the glenoid fossa by contracting the masseter (deep belly), and the temporalis (horizontal fibres).
• discuss the action of the temporomandibular joint (TMJ) - lateral excrusion:

  lateral pterygoid + medial pterygoid on one side contract to move the mandible to the opposite side.
• discuss the action of the temporomandibular joint (TMJ) - protrusion:

  both lateral pterygoids contract simultaneously.
• discuss the action of the temporomandibular joint (TMJ) - retrusion:

  horizontal fibres of temporalis contract.
• list the supporting structures of the TMJ:

  • capsule
  • lateral ligament
  • sphenomandibular ligament
  • stylo-mandibular ligament
• recognize and list components of the TMJ:

  temporal bone:

  • post-glenoid process (furthest away from the teeth)
  • articular fossa (dome shaped)
  • articular eminence (projection closest to the teeth)

  the mandibular condyle

  the articular disc

  the capsule

  supporting ligaments and muscles

  nerve supply: auriculotemporal branch: mandibular division of the trigeminal nerve.
• Lateral Pterygoids


  
  
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  Muscles that protrude the jaw, contracting simultaneously.