2- Articular Cartilage

Question 1

What is articular cartilage?

Answer 1

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.

Question 2

What are the 3 components of the ECM?

Answer 2

water, proteoglycans, and collagens.

Question 3

What type of tissue does not have blood vessels, lymphatics or nerves?

Answer 3

Articular cart.

Question 4

What is the function of the superficial tangential zone of articular cart?

Answer 4

forms almost frictionless gliding surface.

Question 5

What are the components of the superficial tangential zone?

Answer 5

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

Question 6

What is the middle/transitional tangential zone, and what is found there?

Answer 6

fibers less organization and chondrocytes are round

Question 7

What is found in the deep zone of articular cart?

Answer 7

i) Collagen fibers are organized vertical to joint surface and chondrocytes are arranged in columnar fashion.
ii) Proteoglycan content highest

Question 8

What is the morphology of the calcified zone of the articular cart?

Answer 8

deepest layer, separating hyaline cartilage from subchondral bone

Question 9

What is the tidemark in the calcified zone of articular cart?

Answer 9

wavy blue line (stains with H&E) w/in calcified zone that separates deep zone from calcified zone

Question 10

What is the pericellular matrix of the ECM?

Answer 10

thin layer that completely surrounds each chondrocyte separating it from the territorial matrix. Contains proteoglycans

Question 11

What is the territorial matrix of the ECM?

Answer 11

surrounds pericellular matrix, characterized by thing collagen fibrils that form a fibillar network that is distinct from the interterritorial matrix.

Question 12

What is the interterritorial matrix of the ECM?

Answer 12

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.

Question 13

Where do chondrocytes come from, again?

Answer 13

derived from mesenchymal cells. During growth these cells generate a large amount of ECM, and maintain the ECM in mature tissue

Question 14

What is the % of water in the articular cart?

Answer 14

65-80%

Question 15

What is the morphology of collagen?

Answer 15

triple helix protein that is the major structural macromolecule of the ECM.

Question 16

What is the type of collagen that makes up 90-95% of cartilage?

Answer 16

type II

Question 17

What are proteoglycans?

Answer 17

complex macromolecules that consist of a protein core with covalently bound polysaccharide (glycosaminoglycan) chain

Question 18

What are glycosaminoglycans (GAGs)?

Answer 18

polysaccharides consisting of long-chain, unbranched, repeating disaccharide units, such as keratin sulfate, dermatan sulfate, and chondroitin sulfate.

Question 19

What makes up 80-90% of proteoglycans in articular cart?

Answer 19

Aggrecans

Question 20

What are aggrecans?

Answer 20

consist of long extended protein core with up to 100 chondroitin sulfate and 50 keratan sulfate GAGs chains covalently attached to protein core.

Question 21

What type of GAG is most prevelent in articular cart?

Answer 21

Chondrotitin sulfate

Question 22

What happens to keratan sulfate as we age?

Answer 22

increases

Question 23

How can articular cart process information from the environment?

Answer 23

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.

Question 24

What is the relationship between joint loading and motion to articular cart?

Answer 24

needed to maintain the normal composition, structure, and mechanical properties of adult articular cartilage.

Question 25

What happens if a joint’s motion is reduced for a long period of time?

Answer 25

degeneration of articular cartilage, b/c if the joint isn’t moving its not moving the synovial fluid which contains nutrients to the cartilage.

Question 26

What is the morphology of immature articular cart?

Answer 26

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.

Question 27

Why are some of the changes in the adult articular cart bad?

Answer 27

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

Question 28

Why does articular cart have a bad ability to repair itself?

Answer 28

scarcity of native cells and lack of blood vessels to import more.

Question 29

Do superficial articular cartilage injuries extend to the bone?

Answer 29

No

Question 30

Do superficial articular cartilage injuries heal?

Answer 30

No

Question 31

Do superficial articular cartilage injuries cause hemmorrhage or inflammation?

Answer 31

No

Question 32

Do superficial articular cartilage injuries have fibrin clots on the exposed surfaces?

Answer 32

Rarely

Question 33

Do superficial articular cartilage injuries have chondrocytes that migrate to the lesion?

Answer 33

No

Question 34

What is the issue without chondrocyte migration to the damaged superficial articular cart?

Answer 34

Since they are not there there, there is no new tissue to repair damage

Question 35

What is the MOI (mechanism of injury) to cause superficial articular cart damage?

Answer 35

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

Question 36

What are osteochondral fractures?

Answer 36

these injuries disrupt the cartilage AND underlying subchondral bone. They undergo repair (mainly the bone though)

Question 37

What is the mechanism to cause osteochondral fractures?

Answer 37

mechanical injury strong enough to damage both cartilage and bone that causes hemorrhage, fibrin clot, and inflammation

Question 38

What is the anatomic/cell response to osteochondral fractures?

Answer 38

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

Question 39

What is the presentation of osteoarthritis?

Answer 39

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.

Question 40

What is the cause of osteoarthritis?

Answer 40

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)

Question 41

True or false: osteoarthritis does not have an inflammatory response

Answer 41

True

Question 42

When does osteoarthritis usually present in your life?

Answer 42

WHEN YOU OLD