Cartilage Flashcards
what are the 3 types of cartilage
hyaline
elastic
fibrocartilage
what is hyaline cartilage
most prevalent cartilage in adults
includes the articular cartilage that covers joint surfaces
- very hard to repair and can’t repair itself
what is elastic cartilage
found in external ear, eustachian tues, end of nose, epiglottis
- more flexible and elastic than hyaline cartilage
what is fibrocartilage
found in intervertebral discs, meniscus, and tendon bone attachments
- can form when hyaline cartilage is damaged (not as good as hyaline)
what is the ECM of cartilage mainly composed of
65-80% = interstitial fluid (mostly water)
20-35% = type II collagen and proteoglycans (mostly aggrecan)
how is ECM produced
by cartilage cells (chondrocytes) that live inside lacunae in cartilage
does cartilage have blood or nerve supply
no
what is the structure of chondrocytes
surrounded by chondron (pericellular capsule)
obtains nutrition from synovial fluid in the joint
what are chondrocytes
<5% of tissue volume
metabolically active
synthesis and degradation of the ECM
no means of communication with each other
why is it important to load cartilage in a cyclic fashion (load and unload)
mechanical compression signals metabolic activty in chondrocytes (ECM production + degradation)
moves synovial fluid around to deliver nutrition to the chondrocytes
what is the function of ECM
responsible for the mechancial properties of cartilage
what are the properties of type II collagen (type present in cartilage)
high tensile stiffness and strength (no compressive strength, only tensile)
50-60% of solid matrix of cartilage (not incl. water)
what are the properties of proteoglycans
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)
what is the interaction between PGs and collagen
collagens form fibrillar network
PGs bind to fibrillar network
water fills molecular framework
- held in by collagen and pushed by PGs
is cartilage homogenous or non homogenous
non homogenous
what are the depth wise variations in cartilage structure
contents of collagens and PGs
orientation of collagen fibres
shape and size of chondrocytes
what are the 4 depth zones of cartilage
superficial, middle, deep, and calcified
what are the relative proportions of collagen through the layers
lowest in deep
increases through middle
highest in superficial
what are the relative proportions of PGs through the layers
lowest in superficial
highest in middle
decreases in deep (not as low as the amount in superficial)
what are the properties of the superficial zone
10-20% of tissue thickness
collagen oriented parallel to the surface (horizontal)
chondrocytes are face up to the surface (like pancakes)
what is the function of the superficial zone of cartilage
decrease friction through lubrication
what are the properties of the middle zone
40-60% of the thickness
randomly arranged collaged (transitional)
chondrocytes are round and randomly distributed
easier to hold onto water
what is the function of the middle zone
best able to resist compression
what are the properties of the deep zone
30% of the thickness
collagen oriented perpendicular to the surface (vertical)
chondrocytes organised in columns
easier to hold onto water
what is the calcified zone
layer of calcified cartialge anchored to underlying subchondral bone
what is a tidemark
transition between cartilage and calcified cartilage seen during staining
what is the function of cartilage
transfer and distribute load between bones to lower joint stress
low friction during articulation
NOT a shock absorber
