TMJ Flashcards
what is the TMJ
The temporomandibular joint, a unique synovial joint between the mandible and the temporal bone, in front of the ear.
describe the movement of the TMJ in:
a) small opening
b) wide opening
c) protrusion
A) acts as a hinge
B) acts as a hinge and slides forward
C) slides forward
describe the movement of the TMJ in lateral excursion
one joint rotates and moves laterally, while the other translates. Eg. right lateral excursion:
- right joint: rotates and lateral movement
- left joint: translates
how is TMJ different from other synovial joints?
it is a unique joint:
- 2 compartment joint spaces (disc)
- movement limited by teeth and contralateral TMJ
- capable of hinge and sliding movements
- fibrous cartilage not hyaline cartilage
what is the glenoid fossa?
- oval depression in the temporal bone
- where the condyle sits
- bounded by temporal bone and auricular eminence
- it is a thin bone so masticatory forces are transmitted through the teeth
what is the condyle?
~ oval outline
- mesial side wider than the lateral side
- lateral pole anterior to medial pole
what is the joint capsule?
- thin and attached to the glenoid fossa
- continuous with the disc
- has 2 layers: the outer fibrous layer and inner synovial membrane
what is the synovial membrane
- the inner aspect of the joint capsule
- secretes synovial fluid in joint spaces which lubricates the joint
what is the lateral ligament
- part of the capsule
- attached to the lateral surface of the auricular eminence and the posterior surface of the condyle
- restricts posterior, lateral and inferior movements
- restricts contralateral medial movement
- limits the extent of a pure hinge movement
accessory ligaments
- stylomandibular ligaments
- sphenomandibular ligament
- pterygoidmandibular raphe
what is the articular disc?
- dense fibrous disc that sits on top of the condyle
- divides the joint into 2 compartments
upper: between disc and temporal bone, acts as slide
lower: between disc and mandible: acts as hinge
what are the 5 zones of the articular disc?
- anterior band
- intermediate band
- posterior band
- anterior extension
- posterior extension (densely innervated and vascular, upper and lower part, upper layer: vascular and elastic, lower layer; fibrous)
describe the innervation of the TMJ
- rich innervation of the capsule but not the disc
- so clicks of the disc may not be painful
- supplied by the mandibular division of the trigeminal nerve
describe the blood supply of the TMJ
- superficial temporal artery
- maxillary artery
what makes the clicking noise in the TMJ
normally the disc sits on top of the condyle, but in anterior disc displacement, the disc moves to the anterior side of the condyle, and when the jaw opens the disc moves back to the top of the condyle, therefore a clicking sound is made.
