18: TMJ and Mastication Flashcards
what type of joint is it?
modified hinge synovial joint
part of mandible that articulates with temporal bone
condyle
part of temporal bone where mandible fits in
mandibular fossa aka glenoid fossa
articular eminence
mandible slides over it when opening wide
articular tubercle
helps to prevent anterior dislocation of TMJ
post-glenoid tubercle
helps to prevent posterior dislocation of the TMJ
joint capsule
covers joint cavity; thin and loose, allows for wide range of motion
articular disc
unique!
fibrocartilaginous biconcave disc which separates the joint cavity into two synovial compartments - superior and inferior synovial compartments - permits a wider range of motion
inferior synovial compartment
hinge like action: head/condylar process of the mandible rotates against the articular disc
superior synovial compartment
gliding motion: articular disc against mandibular fossa
lateral/temporomandibular ligament
thickening of lateral part of TMJ articular capsule - gives it lateral strength. w/ the post glenoid tubercle, it helps to prevent posterior dislocation
sphenomandibular ligament
- accessory ligament
- goes from spine of sphenoid bone to lingula of mandible
- limits distension in an inferior direction
- protects inferior alveolar nerve/vasculature passing through mandibular foramen
stylomandibular ligament
- weakest and least protective of TMJ ligaments
- limits excessive opening (inferior distension and protrusion) of mandible
- a specialized, reinforced band of cervical fascia
- styloid process to angle of mandible
- boundary b/w parotid and submandibular salivary glands
condylodiscal ligaments
- intrascapular support structures at medial and lateral poles of mandibular condyles (blend in with connective tissue of the articular disc)
- help keep proper alignment of TMJ articular disc w/ condyle
muscles of mastication
lateral pterygoid
medial pterygoid
temporalis
masseter
accessory muscles of mastication
digastric (anterior and posterior bellies) mylohyoid geniohyoid infrahyoid muscles etc...
translation of the TMJ
occurs in the superior synovial compartment - condylar head glides over the articular eminence
depression
opening of mouth; mediated by lateral pterygoid, gravity, suprahyoid and infrahyoid mm.
gliding/rotational movement by both condyles
elevation
closing of mouth; mediated by temporalis, masseter, medial pterygoid
gliding/rotational movement by both condyles
protrusion/protraction
anterior gliding movement of both condyles/the TMJ
mediated by lateral pterygoid, medial pterygoid (assists), masseter superficial head (assists)
retrusion/retraction
posterior gliding movement of both condyles/the TMJ
mediated by temporalis m (posterior/horizontal fibers), masseter deep head (assists)
lateral deviation
side to side grinding and chewing motions - different actions at each condyle
mediated by unilateral action of any of the four muscles of mastication; i.e. unilateral (movement on one side) action of the lateral pterygoid results in mandibular deviation to the contralateral (opposite) side
blood supply to TMJ
primarily: superficial temporal a.
contributions from: deep auricular a. and anterior tympanic a.
there is no vascular supply or sensory innervation to the
central portion of the articular disc of the TJM
otherwise there would be bleeding and pain every time we used our jaw!
