2- Articular Cartilage Flashcards
What is articular cartilage?
tissue that forms the opposing articulating surfaces of synovial joints provides the surfaces with a low friction, lube, and wear characteristics that make possible painless movement.
What are the 3 components of the ECM?
water, proteoglycans, and collagens.
What type of tissue does not have blood vessels, lymphatics or nerves?
Articular cart.
What is the function of the superficial tangential zone of articular cart?
forms almost frictionless gliding surface.
What are the components of the superficial tangential zone?
i) Collagen fibrils arranged parallel to surface, chondrocytes are elongated with axis parallel to surface
ii) Proteoglycan content is lowest
iii) Water content is highest
What is the middle/transitional tangential zone, and what is found there?
fibers less organization and chondrocytes are round
What is found in the deep zone of articular cart?
i) Collagen fibers are organized vertical to joint surface and chondrocytes are arranged in columnar fashion.
ii) Proteoglycan content highest
What is the morphology of the calcified zone of the articular cart?
deepest layer, separating hyaline cartilage from subchondral bone
What is the tidemark in the calcified zone of articular cart?
wavy blue line (stains with H&E) w/in calcified zone that separates deep zone from calcified zone
What is the pericellular matrix of the ECM?
thin layer that completely surrounds each chondrocyte separating it from the territorial matrix. Contains proteoglycans
What is the territorial matrix of the ECM?
surrounds pericellular matrix, characterized by thing collagen fibrils that form a fibillar network that is distinct from the interterritorial matrix.
What is the interterritorial matrix of the ECM?
largest of matrix regions and contributes most of the material properties of the articular cartilage, encompasses area between the territorial matrices, and it contains large collage fibers and most of the proteoglycans.
Where do chondrocytes come from, again?
derived from mesenchymal cells. During growth these cells generate a large amount of ECM, and maintain the ECM in mature tissue
What is the % of water in the articular cart?
65-80%
What is the morphology of collagen?
triple helix protein that is the major structural macromolecule of the ECM.
What is the type of collagen that makes up 90-95% of cartilage?
type II
What are proteoglycans?
complex macromolecules that consist of a protein core with covalently bound polysaccharide (glycosaminoglycan) chain
What are glycosaminoglycans (GAGs)?
polysaccharides consisting of long-chain, unbranched, repeating disaccharide units, such as keratin sulfate, dermatan sulfate, and chondroitin sulfate.
What makes up 80-90% of proteoglycans in articular cart?
Aggrecans
What are aggrecans?
consist of long extended protein core with up to 100 chondroitin sulfate and 50 keratan sulfate GAGs chains covalently attached to protein core.
What type of GAG is most prevelent in articular cart?
Chondrotitin sulfate
What happens to keratan sulfate as we age?
increases
How can articular cart process information from the environment?
since cartilage is aneural, chondrocytes derive info from the mechanical stresses and strains that act on their membranes as a result of physical forces applied to the tissue. The most important are joint motion and loading.
What is the relationship between joint loading and motion to articular cart?
needed to maintain the normal composition, structure, and mechanical properties of adult articular cartilage.
What happens if a joint’s motion is reduced for a long period of time?
degeneration of articular cartilage, b/c if the joint isn’t moving its not moving the synovial fluid which contains nutrients to the cartilage.
What is the morphology of immature articular cart?
thicker, more cellular, and appears blue-white, b/c of vascular structures in the underlying immature bone. It is thicker b/c immature cartilage it has 2 tasks, serve as a cartilaginous articular surface for joint and to be a source for endochondral ossification of the underlying bone.
Why are some of the changes in the adult articular cart bad?
undergoes changes that increase the risk of degeneration, tissue tensile strength of the superficial cartilage layer decreases and the ability of chondrocytes to maintain and restore the tissue diminishes
Why does articular cart have a bad ability to repair itself?
scarcity of native cells and lack of blood vessels to import more.
Do superficial articular cartilage injuries extend to the bone?
No
Do superficial articular cartilage injuries heal?
No
Do superficial articular cartilage injuries cause hemmorrhage or inflammation?
No
Do superficial articular cartilage injuries have fibrin clots on the exposed surfaces?
Rarely
Do superficial articular cartilage injuries have chondrocytes that migrate to the lesion?
No
What is the issue without chondrocyte migration to the damaged superficial articular cart?
Since they are not there there, there is no new tissue to repair damage
What is the MOI (mechanism of injury) to cause superficial articular cart damage?
high-level forces that causes ruptures or tears, also by increasing load on adjacent tissue large articular surface defects may cause degeneration of normal cartilage
What are osteochondral fractures?
these injuries disrupt the cartilage AND underlying subchondral bone. They undergo repair (mainly the bone though)
What is the mechanism to cause osteochondral fractures?
mechanical injury strong enough to damage both cartilage and bone that causes hemorrhage, fibrin clot, and inflammation
What is the anatomic/cell response to osteochondral fractures?
fibrin clot fill the injury site and inflammation cells migrate to clot. The injury causes bone to release rowth factors and other proteins that mediate repair, platelets release platelet derived growth factor and transforming GF-β
What is the presentation of osteoarthritis?
joint pain, joint effusions, and deformity. There may be fissuring and focal erosive cartilage lesions, cartilage loss and destruction, subchondral bone sclerosis, and cyst/osteophyte formation in joint.
What is the cause of osteoarthritis?
Idiopathic (unknown cause), or may result from injuries/infection or be hereditary, developmental, metabolic, or neurologic. It is a progressive loss of articular cartilage, accompanied by attempted repair, remodeling, and sclerosis of subchondral bone (which may lead to cysts/osteophytes)
True or false: osteoarthritis does not have an inflammatory response
True
When does osteoarthritis usually present in your life?
WHEN YOU OLD
