Articular Cartilage

Question 1

What are the 3 types of cartilage?

Answer 1

hyaline
elastic
fibrocartilage

Question 2

What does hyaline cartilage do?

Answer 2

covers tha articular surface of bones in synovial joints

Question 3

What does elastic cartilage do?

Answer 3

forms structures like the outer ear, epiglottis

Question 4

What structures are made from fibrocartilage?

Answer 4

symphysis pubis, intervertebral discs

Question 5

What is articular cartilage?

Answer 5

a form of hyaline cartilage found on the articulating ends of bones in synovial joints

Question 6

What are the two main roles of articular cartilage?

Answer 6

shock absorption

reducing joint friction

Question 7

What is the gross composition of articular cartilage?

Answer 7

organic matrix of non-cellular material interspersed with cells and fluid

Question 8

What is the organic matrix of non-cellular material in cartilage made from?

Answer 8

Collagen organised into fine collagen fibrils

Question 9

What fluid is present around the collagen fibrils?

Answer 9

concentrated proteoglycans

Question 10

Which layer of cartilage are proteoglycans most abundant?

Answer 10

middle layer

less concentrated towards bone

Question 11

What is the name for the sparsely distributed cells of articular cartilage?

Answer 11

chondrocytes

Question 12

What happens to the abundance of chondrocytes as you move towards the bone?

Answer 12

increases

Question 13

What is made by chondrocytes?

Answer 13

collagen (the organic matrix)

Question 14

What is the interstitial fluid in the matrix made from?

Answer 14

water

Question 15

What are the 3 zones of cartilage called?

Answer 15

superficial tangential
middle
deep

Question 16

What is the structure of the superficial tangential zone?

Answer 16

tightly woven collagen fibrils in sheets parallel to the articular surface

chondrocytes are oblong with parallel axes to the surface

Question 17

What is the structure of the middle zone?

Answer 17

more randomly arranged collagen but broadly arranged parallel to the articular surface

less densely packed to accommodate proteoglycans high concentration

chondrocytes are circular and randomly distributed

Question 18

What is the structure of the deep zone?

Answer 18

collagen fibrils in large fibre bundles that are anchored in the underlying bone tissue - attaching cartilage to bone.

chondrocytes are aligned perpendicular to the articular surface

Question 19

What is the tidemark?

Answer 19

the interface between a thin layer of calcified cartilage below the deep zone which gradually merges into the subchondral bone.

Question 20

What does viscoelastic behaviour mean?

Answer 20

It means that the response of the material varies according to the length of time it is loaded and the rate at which it is loaded.

Question 21

What happens when a load is removed from a viscoelastic material?

Answer 21

it will return to its original shape - but not immediately

Question 22

What is creep?

Answer 22

Creep occurs when a viscoelastic material is subject to a constant load - initially rapid deformation occurs, followed by slowly increasing deformation .

Question 23

Why does creep occur?

Answer 23

During initial deformation, fluid is rapidly pushed out of the cartilage. As the fluid is pushed out the rate of expulsion decreases, as does the fluid remaining until equilibrium is reached

Question 24

What is stress relaxation?

Answer 24

Stress relaxation occurs when a viscoelastic material is kept at a constant deformation - if a material is deformed to a certain degree the load required to maintain that deformation decreases with time

Question 25

Why does stress relaxation occur?

Answer 25

Stress relaxation occurs as during initial deformation fluid is forced out of the joint - due to friction of forcing out fluid a large load is needed.

during stress relaxation the fluid is no longer being forced out so the stress required to maintain a deformation decreases

Question 26

What are the 3 types of lubrication?

Answer 26

elastohydrodynamic
boosted
boundary

Question 27

What is elastohydrodynamic lubrication?

Answer 27

This happens when two surfaces are lubricated by a film of fluid as they move relative to one another

Question 28

What is squeeze film lubrication?

Answer 28

elastohydrodynamic lubrication when surfaces are compressed together

Question 29

What is hydrodynamic lubrication?

Answer 29

lubrication when two surfaces slide over each other forming a wedge of fluid which generates a lifting pressure

Question 30

What is boosted lubrication?

Answer 30

when two surfaces are forced together over a period of time, eventually the lubricant will be completely depleted

the articular cartilage surface is selectively permeable - so small molecules are forced through, leaving only large solute molecules behind

this leaves a thick, enhanced lubricant capable of supporting large loads

Question 31

What is boundary lubrication?

Answer 31

Boundary lubrication is when loads are large enough and sustained for long enough, the fluid will will become completely depleted.

lubricant molecules attach themselves to the articular surfaces and create a BOUNDARY LAYER like a non-stick frying pan.

Question 32

What protein is involved in boundary lubrication?

Answer 32

lubricin