Chapter 61 - Articular Cartilage and Osteoarthritis

Question 1

articular cartilage is primarily composed of what type of collagen?

Answer 1

type II collagen - 95%
others:
- Type VI: increased in early stages of OA
- type X - associated with cartilage calcification (calcified deep zone of cartilage)
- V, IX, and XI

Question 2

where else is type II collagen found in the body?

Answer 2

Nucleus Pulposis is primarily Type II collagen

Annulus fibrosis is Type 1 collagen

Question 3

what does collagen do for articular cartilage?

Answer 3

provides shear and tensile strength

Question 4

what do proteoglycans do for cartilage?

Answer 4

provide COMPRESSIVE strength

Question 5

what are proteoglycans composed of

Answer 5

repeating disaccharide subunits - glycosaminoglycans
- chondroitin sulfate (a GAG)
with age: chondroitin-4-sulfate decreases, chondroitin-6-sulfate stays constant
- keratan sulfate (a GAG)
with age: keratin sulfate increases

Question 6

Layers of articular cartilage

Answer 6

1. superficial zone: collagen fibers paralel to surface
2. transitional zone: collagen fibers randomly oriented
3. deep zone: collagen fibers perpendicularly oriented
4. tidemark/calcified zone

Question 7

features of the superficial zone of cartilage

Answer 7

• low proteoglycan content
• disc shaped chondrocytes
• collagen an chondrocytes parallel to articular surface - resist shear force
• high collagen content
• high water content

Question 8

features of the middle zone of cartilage

Answer 8

thicker, randomly oriented collagen
- round chondrocytes
- lots of proteoglycans
- resists compressive forces

Question 9

features of the deep zone of cartilage

Answer 9

perpendicular collage
columnar chondrocytes
high proteoglycan content
resists shear forces during movement

Question 10

features of the calcified zone

Answer 10

deep to the tidemark
very low proteoglycan content
lots of hydroxyapatite
hypertrophic chondrocytes produce type X collagen and alkaline phosphatase helping to mineralize the ecm

Question 11

breakdown of cartilage matrix in norml turnover is stimulated by what?

Answer 11

activation of proteolytic enzymes (proteinases)

Question 12

metalloproteinases

Answer 12

collagenase, stromelysin, gelatinase
- produced as inert proteins and require enzymatic activation

Question 13

lubricin role in the joint

Answer 13

key lubricant of synovial fluid
binds to hylauronic acid