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UKCD Histo TMJ
learning objectives for TMJ
Question | Answer |
---|---|
Classify the TMJ as a specific type of synovial joint. | Ginglymus joint, a sliding hinge joint. |
How many synovial cavities are present in the TMJ? | There are two cavities: a superior and inferior. |
What structure separates/ creates these two cavities? | An intraarticular disc (meniscus). |
Do these synovial cavities communicate? | No. There is no communication between synovial cavities. |
How is the intra-articular disc (meniscus) attached/ held within the synovial cavity? | anchored medially $ laterally to the fibrous capsule and anteriorly with the superior head of the lateral pterygoid muscle. The synovial membrane forms a continuous attachment around the entire periphery of the disc forming two isolated synovial cavities. |
How do the articular surfaces of this joint differ from those of other synovial joints? | The articular surfaces of the TMJ are lined by dense, avascular fibrous connective tissue - not articular cartilage. |
List the 4 zones of the articular surface of the TMJ? | I - articular surface; II - proliferative zone; III - fibrocartilagenous zone; and IV - zone of calcified cartilage. |
How are the collagen fiber bundles of Zone 1 oriented? | Collagen fibers of Zone I are closely packed and oriented parallel to the articular surface. |
In Zone 1, where are fibroblast found? Never found? | Fibroblasts of Zone I are found between fiber bundles but never on the articular surface. |
What is the lamina splendens? | A 1-3 micrometer thick layer that separates collagen fiber bundles from the joint cavity. It forms the articular surface of the TMJ. |
How do the articular surfaces of the TMJ differ with age? | The proliferative zone of the articular surface becomes much reduced with age and the cartilage underlying this zone converts from hyaline to fibrocartilage. The surface fibrous layer remains unchanged. |
What is the function of synovial villi? How do these structures vary with age? | Thought to provide additional membrane for joint expansion although their number increases with age. |
What surfaces are lined by synovial membrane? | All non-articular surfaces of the interior aspect of both TMJ cavities. |
How are synovial membranes classified? | By the type of connective tissue that they overly (fibrous, areolar, etc.). |
List the two layers of the synovial membrane? | The superficial cellular intima that rests on the vascular subintima. |
Identify the two cell types found in the cellular intima. What is the function of each? | Fibroblast -like cells that secrte synovial fluid and macrophage-like cells that remove debris from the synovial cavity. |
How many layers of cells are present in the intima? | One to four layers of synovial cells. |
How are the cells in the intima attached to one another to form a layer? | Synovial cells are embedded in an amorphous matrix. Junctional complexes and a basement membrane are not involved. |
In what specific type of matrix are these cells embedded? | The amorphous matrix contains no fibers (collagen) |
What are the physical properties of synovial fluid? | Viscous, elastic and plastic - specialized for friction-free movement of articular surfaces. |
Of what is the articular disc of the TMJ initially composed? | A dense avascular fibrous connective tissue. |
What happens to the articular disc with increasing age? | With age the dense fibrous CT of the intraarticular disc is replaced by fibrocartilage. |
Which region of the disc is highly vascular? Why? | The posterior region of the disc is highly vascular while the central region is avascular due to its major role in articulation. |
Are the synovial membrane and articular disc innervated? | The synovial membrane and articular disc (meniscus) are not innervated . |