Cartilage

Question 1

what are the 3 types of cartilage

Answer 1

hyaline
elastic
fibrocartilage

Question 2

what is hyaline cartilage

Answer 2

most prevalent cartilage in adults
includes the articular cartilage that covers joint surfaces
- very hard to repair and can’t repair itself

Question 3

what is elastic cartilage

Answer 3

found in external ear, eustachian tues, end of nose, epiglottis
- more flexible and elastic than hyaline cartilage

Question 4

what is fibrocartilage

Answer 4

found in intervertebral discs, meniscus, and tendon bone attachments
- can form when hyaline cartilage is damaged (not as good as hyaline)

Question 5

what is the ECM of cartilage mainly composed of

Answer 5

65-80% = interstitial fluid (mostly water)
20-35% = type II collagen and proteoglycans (mostly aggrecan)

Question 6

how is ECM produced

Answer 6

by cartilage cells (chondrocytes) that live inside lacunae in cartilage

Question 7

does cartilage have blood or nerve supply

Answer 7

no

Question 8

what is the structure of chondrocytes

Answer 8

surrounded by chondron (pericellular capsule)
obtains nutrition from synovial fluid in the joint

Question 9

what are chondrocytes

Answer 9

<5% of tissue volume
metabolically active
synthesis and degradation of the ECM
no means of communication with each other

Question 10

why is it important to load cartilage in a cyclic fashion (load and unload)

Answer 10

mechanical compression signals metabolic activty in chondrocytes (ECM production + degradation)
moves synovial fluid around to deliver nutrition to the chondrocytes

Question 11

what is the function of ECM

Answer 11

responsible for the mechancial properties of cartilage

Question 12

what are the properties of type II collagen (type present in cartilage)

Answer 12

high tensile stiffness and strength (no compressive strength, only tensile)
50-60% of solid matrix of cartilage (not incl. water)

Question 13

what are the properties of proteoglycans

Answer 13

25-35% of solid matrix of cartilage
- negatively charged and therefore have mutual repulsion (always want to push on each other and resist compression)
- provide high compressive strength (cartilage would have no compressive strength without these)

Question 14

what is the interaction between PGs and collagen

Answer 14

collagens form fibrillar network
PGs bind to fibrillar network
water fills molecular framework
- held in by collagen and pushed by PGs

Question 15

is cartilage homogenous or non homogenous

Answer 15

non homogenous

Question 16

what are the depth wise variations in cartilage structure

Answer 16

contents of collagens and PGs
orientation of collagen fibres
shape and size of chondrocytes

Question 17

what are the 4 depth zones of cartilage

Answer 17

superficial, middle, deep, and calcified

Question 18

what are the relative proportions of collagen through the layers

Answer 18

lowest in deep
increases through middle
highest in superficial

Question 19

what are the relative proportions of PGs through the layers

Answer 19

lowest in superficial
highest in middle
decreases in deep (not as low as the amount in superficial)

Question 20

what are the properties of the superficial zone

Answer 20

10-20% of tissue thickness
collagen oriented parallel to the surface (horizontal)
chondrocytes are face up to the surface (like pancakes)

Question 21

what is the function of the superficial zone of cartilage

Answer 21

decrease friction through lubrication

Question 22

what are the properties of the middle zone

Answer 22

40-60% of the thickness
randomly arranged collaged (transitional)
chondrocytes are round and randomly distributed
easier to hold onto water

Question 23

what is the function of the middle zone

Answer 23

best able to resist compression

Question 24

what are the properties of the deep zone

Answer 24

30% of the thickness
collagen oriented perpendicular to the surface (vertical)
chondrocytes organised in columns
easier to hold onto water

Question 25

what is the calcified zone

Answer 25

layer of calcified cartialge anchored to underlying subchondral bone

Question 26

what is a tidemark

Answer 26

transition between cartilage and calcified cartilage seen during staining

Question 27

what is the function of cartilage

Answer 27

transfer and distribute load between bones to lower joint stress
low friction during articulation
NOT a shock absorber