histology of the TMJ

Question 1

Development of the dif parts of the TMJ

directions of development

Answer 1

develop separate from one another, can lead to abnormalities if some parts are over or under developed
usually develop in an anterior-posterior direction with lateral flaring as well

Question 2

inn of the TMJ (functions)

Answer 2

Question 3

TMJ joint classification
each bone covered with?
both bones are surrounded with? 
what is cavity filled with? derived from? 
what separates the bones?

Answer 3

The TMJ is classified as a synovial sliding-ginglymoid
(hinged) joint:
Synovial joints permit movement between two bones.

 Each bone is covered by hyaline cartilage.
 The two bones are united and surrounded by a fibrous capsule thereby creating a joint cavity.
 The joint cavity is filled with synovial fluid (approximately 1mL) that is derived from villus cells which line the internal surface of the capsule.
 Also present is a fibrous disc which separates the bones

Question 4

TMJ development
type of bone formation
growth capacity?
difference from long bones?

Answer 4

 Both the condylar neck and head develop by endochondral ossification.
 The condylar head develops by endochondral ossification, and has multidirectional growth capacity.

Unlike long bones of the body the cartilage cells in the condylar head and neck do not exhibit ordered columns (epiphyseal growth plates).

Question 5

gemeral anatomy of the TMJ
bones
fibrous capsule
lateral pterygoid

Answer 5

Bones of the TMJ are the glenoid fossa and the mandibular condyle.
Fibrous capsule: covers the joint
Superior and inferior heads of the lateral pterygoid muscle
• Superior head attaches to the joint capsule and articular disc (a.k.a. meniscus)
• Inferior head attaches to the condylar neck in the pterygoid fovea

Question 6

articulating surfaces of the TMJ covered with?

exhibit what with increased age?

Answer 6

The articulating surfaces are covered with a layer of fibrous tissue.
With increasing age, the deeper portions of the fibrous covering may exhibit islands of cartilage

Question 7

condylar head cellularity w age

Answer 7

decreases

Question 8

articular disc cellularity with age

Answer 8

increases

Question 9

Retrodiscal Connective Tissue (a.k.a. bilaminar zone):
insertion of fibers?
articulation here?

Answer 9

Comprised of collagen and elastic fibrous connective tissue, fat cells, and is highly vascular.

Elastic fibers from this bilaminar zone insert into the petrotympanic fissure.

allows anterior movement of the joint, flexible
no articulation here

Question 10

anterior dislocation of the disc and articulation

disc attachment

Answer 10

The disc is attached to the medial and lateral surfaces of the condyle, but not the temporal bone.

when the mandible moves, the disc moves as well, traveling over the anterior surface of the articular fossa.

All articulation is on the fibrous portion of the disc. This dense area also restricts the posterior movement of the mandible, and maintains the condyle in the anterior part of the glenoid fossa.

The vascular retrodiscal area allows the mandible to move freely in an anterior direction.

Question 11

collagen fiber orientations of the roof of the glenoid fossa and posterior articular tubercle slope

Answer 11

roof of the fossa: vertical

posterior slope of the articular tubercle: horizontal

Question 12

advantage of multidirectional collagen fibers of the glenoid fossa

Answer 12

makes area more robust

Question 13

articular line of the glenoid fossa

Answer 13

junction between the horizontal and vertically oriented collagen

Question 14

synovial membrane

Answer 14

 The synovial membrane lines the inner surface of the fibrous capsule
 The TMJ synovial membrane consists of three distinct layers of tissue:
• The most peripheral (external) layer=fibrous capsule of the joint
• The intermediate layer=vascular subintima
• The most internal layer=intimal layer

Question 15

cell types of the intimal layer

Answer 15

Type A Synovial Cells:
 Macrophage-like cells that exhibit phagocytic functions and are capable of producing inflammatory cytokines, e.g., IL-1, IL-6, IL-8, and TNF-α

Type B synovial Cells:
 Fibroblast-like cells that synthesize hyaluronate which
is a major component of the synovial fluid in both the
superior and inferior compartments of the joint.

Question 16

inflammatory joint disease, effect on type A cells
required cytokines
affect on condlye

Answer 16

Chronic or acute joint trauma may cause the Type A synovial cells fuse/transformation into multinucleated
giant cells that exhibit osteoclastic-like functions (i.e. resorption of bone and cartilage). Thus, the articular surfaces, including the joint meniscus, are subjected to cellular mediated surface resorption
occurs with high levels of IL-1, IL-6, IL-8, and TNF-A

If the inflammatory response is of sufficient intensity and duration, bone and cartilage resorption can also take place within the spongiosa of the condylar head and subjacent condylar neck.
Thus, resorption can actually occur simultaneously on both the external and internal surfaces of the condyle.

Question 17

arachdionic acid pathway

Answer 17

Question 18

inflammatory joint disease pathway diagram

Answer 18

Question 19

arthritic degeneration
internal derangement?
cells?
restrodiscal tissue?

Answer 19

With these chronic inflammatory changes, osteophytes are noted on the condylar heads.

decreased vascularity is found in the retrodiscal area, leading to pain in function.

Internal Derangement: the disc is trapped in the anteromedial position, causing limited opening, pain, and “clicking” upon opening

Question 20

ankylosis from untreated fracture

Answer 20

Loss of articular coverings and synovial membranes, leading to direct bone-to-bone fusion