Cartilage

Question 1

function of cartilage

Answer 1

movement, gliding, limiting friction, distribute loads over a wide area and absorb shock

Question 2

structure of articular cartilage

Answer 2

has specialized form of hyaline cartilage that covers the ends of all bones, surface appears smooth but actually has pits and ridges

Question 3

Chondrocytes

Answer 3

account for 10% of tissue volume and are responsible for producing and maintaining the organic composition of articular cartilage (collagen, proteoglycans and glycoproteins)

Question 4

Collagen makes up what net weight of cartilage

Answer 4

10-30%

Question 5

Proteoglycans make up what net weight of cartilage

Answer 5

3-10%

Question 6

what is the predominant factor to net weight in cartilage

Answer 6

water, 60-87% (along with inorganic salts)

Question 7

what is the predominant collagen type in articular cartilages

Answer 7

type II, resists compression

Question 8

Collagen function in cartilage

Answer 8

provides the ECM framework and tensile strength of articular cartilage

Question 9

are proteoglycans positive or negatively charged?!

Answer 9

negative they are polyionic

Question 10

compression of PGs results in

Answer 10

increased repulsive forces between the PGs and increased compressive stiffness

Question 11

when tissue is loaded… up to ____ % of water can be moved

Answer 11

70

Question 12

Nutrition of cartilage means

Answer 12

cartilage becomes less stiff and more permeable due to increased water content

Question 13

Superficial/tangential zone

Answer 13

structure: sheets of fine, densely packed fibers randomly woven in planes PARALLEL to the articular surface
function: resists shearing forces on the surface by decreasing friction and distributing the force
resists compression with type 1 collagen

Question 14

Middle zone

Answer 14

fibers are randomly oriented and homogenously dispersed to surround the chondrocytes

Question 15

deep zone

Answer 15

collagen fibers are oriented with pattern in tightly packed bundles, fibers are perpendicular to the surface

Question 16

tidemark

Answer 16

interface b/w articular cartilage and the calcified cartilage beneath is, anchors the cartilage to the underlying bone

Question 17

where does articular cartilage show less healing when injured

Answer 17

above the tidemark

Question 18

why does below the tidemark heal faster?

Answer 18

the healing/inflammation from the subchondral bone occurs so there is increased blood flow and faster healing than a superficial wound

Question 19

Subchondral bone

Answer 19

highly organized
trabecular bone interlocks and align in a matrix configuration
designed to counteract the line of application of the average load to the joint

Question 20

What provides the nutrition to articular cartilage

Answer 20

synovial fluid through compression and decompression of the cartilage surface (we need non-destructive motion of the joint) AKA MOVEMENT

Question 21

where is permeability of AC the highest

Answer 21

near the joint line

Question 22

where is permeability the lowest in AC

Answer 22

in the deep zone

Question 23

Permeability changes with deformation

Answer 23

as it is compressed, the permeability decreases

articular cartilage is highly porous but very low in permeability

Question 24

how much synovial fluid is in the synovial space of the knee

Answer 24

about 4 mL

Question 25

Function of synovial fluid

Answer 25

exchange metabolites with the vasculature in synovial lining, nutrients, contains Lubrican and hyaluronic acid to add viscosity decreases friction, nutrition and distributes forces

Question 26

Rapid loading

Answer 26

there is no time for the fluid to flow out so pressure from the interstitial fluid rather than the solid matrix, supports a significant portion of the load

Question 27

slow loading

Answer 27

fluid pressure decreases and STRESS increases in the solid matrix the negatively charged GAGS push away

Question 28

CREEP

Answer 28

sustained load articular cartilage deforms under a constant load (like braces) as the rate of displacement slows, fluid flow slows too equilibrium= displacement is constant and fluid flow has stopped (takes a several thousand seconds 4-6 hours

Question 29

what contributes to the stress rise

Answer 29

associated with fluid exudation

Question 30

stress relaxation=

Answer 30

fluid redistribution within the porous solid matrix

Question 31

Where does the collagen resist TENSION

Answer 31

collagen in the superficial tangential zone

Question 32

extracellular framework and tensile strength

Answer 32

provides the joint cartilage with a tough, wear resistant, protective skin

Question 33

Monolayer of synovial fluid

Answer 33

it is absorbed on each surface so there is no direct contact surface to surface which prevents surface wear

Question 34

Fluid Film

Answer 34

thin layer of freestanding lubricant between sliding surfaces to decrease surface to surface contact area

Question 35

what does fluid film rely on

Answer 35

viscosity

Question 36

Hydrodynamic fluid film

Answer 36

occurs when rigid bearing surfaces which are not parallel and are separated by a fluid film SLIDING IS TANGENTIAL

Question 37

Squeeze film

Answer 37

occurs when the bearing surfaces are moving PERPENDICULARLY towards each other viscosity of fluid produces pressure that tends to force the lubricant out

Question 38

weeping

Answer 38

joint load is borne by hydrostatic pressure of the synovial fluid escaping from the cartilage

Question 39

boosted lubrication

Answer 39

as the load is applied, synovial fluid is trapped in the cartilage, toward the subchondral bone at the point of contact

Question 40

causes to articular cartilage degeneration

Answer 40

``` increased stress wear and tear high load over extended period of time chemical insults metabolic factors ```

Question 41

Histological changes of articular cartilage

Answer 41

increased water content secondary to freeing of GAGs loss of PGs leading to decreased mechanical properties PGs less dense between fibers (poor matrix support)

Question 42

Interfacial adhesive wear

Answer 42

fragments stick and pull away from the surface

Question 43

interfacial abrasive wear

Answer 43

soft material scraped by harder material

Question 44

fatigue wear

Answer 44

accumulation of microscopic damage under repetitive stresses

Question 45

superficial cartilage trauma

Answer 45

no inflammatory response | minimal healing

Question 46

healing of deep cartilage lesion

Answer 46

local bleeding from subchondral bone produces hematoma that becomes organized and invaded by granulation tissue flakes of the cartilage break away into the joint space which decreases the energy absorbing function and stimulating the subchondral bone plate

Question 47

immobilization on articular cartilage

Answer 47

decreased PG aggregation increased water content AC is softer and weaker