Week 12 - Temporomandibular Joint Flashcards
Describe mandible growth
different parts grow in congruence with each other (independently but at the same time) but in general tends to happen in anterior-posterior direction as well as in a flaring direction
What happens in underdeveloped ramus/body?
steeper incline/angle of jaw, can lead to crowding issues
What happens in an overdeveloped ramus/body?
Flat angle of jaw
What are ruffini corpuscles used for?
Proprioception (where mandible is in space)
What are pacinian corpuscles used for?
dynamic mechanoreception (chewing)
What are golgi tendon organs used for?
static mechanoreception (rest)
What are free nerve endings used for?
detect pain
What is the TMJ classified as?
synovial sliding-ginglymoid joint
What does synovial permit?
permits movement between two bones
What does sliding describe?
the second part of jaw opening, sliding anterior of the condyle over the glenoid fossa
What does ginglymoid describe?
the first part of opening, hinge portion
What is the joint cavity filled with and what is it derived from?
filled with synovial fluid (1 mL) that is derived from villus cells which line the internal space of the capsule
What does the fibrous disc separate?
The bone preventing damage
How do the condylar neck and head develop?
By endochondral ossification
What is the multidirectional growth capacity?
unlike long bones of the body, which also develop by endochondral ossification, the cartilage cells in the condylar head and neck do not exhibit ordered columns (characteristic of the epiphyseal growth plates in long bones)
What encapsulates the entire joint?
Fibrous capsule
What attaches to joint capsule and articular disc (meniscus)?
Superior lateral pterygoid
What attaches to condylar neck in pterygoid fossa?
Inferior lateral pterygoid
What is the glenoid fossa?
bony part of the temporal bone that allows for articular surface of mandibular condyle to fit in
What does the glenoid fossa have?
collagen fiber going in multiple directions allowsing for a more robust surface of articulation (more friction and more prone to damage)
What is the posterior slope of the TMJ’s articular emininance inner perpendicular collagen fibers responsible for?
resisting compression of the mandibular condyle against the articular surface of bone
What are articulating surfaces covered with?
A layer of fibrous tissue
What happens to articulating surfaces with increase age?
the deeper portion of the fibrous covering may exhibits islands of cartilage
What happens to condylar heads with age?
the condylar head becomes less cellular
What happens to the articular disc with age?
becomes more cellular (chondrocytes invading) with age
What is the retrodiscal connective tissue (bilaminar zone) comprised of?
collagen and elastic fibrous connective tissue, fat cells, and is highly vascular
What does the composition of the retrodiscal connective tissue allow for?
the mandible to move freely in an anterior motion
Where is there no articulation?
There is NO articulation between the Retrodiscal connective tissue and the condyle
Where do elastic fibers insert posteriorly?
into the petrotympanic fissure
Where do elastic fibers insert into anteriorly?
into the superior head of the lateral pterygoid
What is the anterior dislocation of the disc attached to?
the medial and lateral surfaces of the condyle, but not the temporal bone
What happens when the mandible moves?
the disc moves as well (traveling over the anterior surface of the articular fossa)
- Movement of the disc back in forth can cause an asymptomatic clicking sound (present in about 70% of the population)
Where is all articulation of the disc on?
Fibrous portion/dense area
What does the dense area of the disc restrict?
the posterior movement of the mandible, and maintains the condyle in the anterior part of the glenoid fossa
Why is the synovial membrane necessary?
presence of sliding movement occurring
Where is the synovial membrane located?
in the inner surface of the fibrous capsule
What are the three layers of the TMJ synovial membrane?
- The most peripheral/external layer is the fibrous capsule of the joint
- The intermediate layer is the vascular subintima
- The most internal layer is termed the intimal layer
What two cell types compose the internal layer?
Type A and type B synovial cells
What are type A synovial cells?
(“trouble makers”) macrophage like cells that exhibit phagocytic functions and are capable of producing inflammatory cytokines
What are examples of type A synovial cells?
Interleukins and tumor necrosis factors
What are type B synovial cells?
(“peace makers”) fibroblast like cells that synthesize hyaluronate
What is hyaluronate?
major component of the synovial fluid in both the superior and inferior compartments of the joint
- major part of slippery synovial fluid that allows for free movement of the joint
What is inflammatory joint disease due to?
type A cells fuse and transform into a multinucleated giant cell
What is the function of multinucleated giant cells?
function like osteoclasts, by resorbing bone and cartilage and elevate cytokines (IL and TNFs) levels
What happens if the inflammatory joint disease is intense enough?
the resorption can take place within spongiosa of head and neck (thus resorption can occur simultaneously on both internal and external surfaces of the condyle)
What kind of inflammatory response is inflammatory joint disease?
circular inflammatory response (the longer it occurs, the more damage it can cause)
Describe the arachidonic acid pathway
Injury to the cell membranes causes release of phospholipids and phospholipase. This is the point where steroids typically begin to help. Arachidonic acid is released where it can break down into lipoxygenase and cyclooxygenase (where NSAIDs can break this pathway)
What do Leukotrienes, prostaglandins and thromboxane’s activate?
“troublemaker” A cells resulting in swelling, pain, and vasoconstriction
Describe the process starting from trauma and ending at tissue destruction?
Trauma -> activation of arachidonic pathway -> leukotrienes, thromboxanes, and prostaglandins activate Type A cells -> increased IL (1,6,8) and TNF (alpha) -> macrophage/osteoclastic activity -> tissue destruction
What is arthritic degeneration?
flattened condylar head occurs due to osteoclastic activity, causing an almost bone-on-bone contact due to lack of cartilage layer
What happens with chronic inflammatory changes?
osteophytes (point) are noted on the condylar heads (pointy nature cuts into discal tissue)
What happens due to degeneration of arthritic tissue?
there is decreased vascularity found in the retrodiscal area, leading to pain on function
What is internal derangement?
disc is trapped in the antero-medial position
What does internal derangement cause?
limited opening, pain, and clicking upon opening (only clicks on one side)
What is ankylosis?
loss of articular coverings and synovial membranes leading to direct bone-to-bone fusion
What is ankylosis result from?
Untreated fracture
What can ankylosis lead to?
specific malocclusion issues
