CARTILAGE Flashcards
What is the function of cartilage
Smooth bearing surface
Flexible interface between bones
Flexible support
Where may we find cartilage
Outer ear
Sternum
Cartilage rings of trachea
How does cartilage grow?
Interstitial growth (from within)
What is the matrix of cartilage like?
No minerals
No blood vessels
No nerves
Different cells, proteins and microstructure to osteoid
Where do we find hyaline/ articular cartilage?
Synovial joints
Sternum
Embryos before bone is formed
What type of collagen does hyaline/ articular cartilage have
Type 2
What is the structure of hyaline/ articular cartilage like?
No blood vessels
No nerves
No lymphatics (not great for repairing itself)
What is the hyaline/ articular cartilage designed to do?
Shock absorber
Withstand and distribute load
Act as an elastic shock absorber
Wear resistance to articular joints
Be self maintaining —> grow and repair itself
What is articular/ hyaline cartilage designed to do?
Withstand and distribute load
Act as an elastic shock absorber
Provide a wear resistant surface to articular joints
Self maintained (grows back slowly)
Where do we find fibrocartilage?
Intervertebral disks
Where tendons attach to bones
What collagen is in the extracellular matrix of fibrocartilage?
Type 1 and 2
What is the structure of fibrocartilage?
Fibrocartilage is a combination of dense regular connective tissue and hyaline cartilage. The chondrocytes are dispersed among the collagen fibers singularly, in rows
Less matrix than in other cartilage types
No perichondrium
What is the function of fibrocartilage?
For tough support or great tensile strength
Where do you find elastic cartilage?
Outer ear
What is difference between hyaline and elastic cartilage
Elastic cartilage has elastin in matrix
Elastin cartilage doesn’t calcify in ageing process like hyaline
What is difference between fibrocartilage and elastic cartilage/
Fibrocartilage has no elastin fibres
Fibrocartilage has no perichondrium
What function of elastic cartilage?
To keep tubes open
What are chondrocytes?
The only cells found in the cartilage
They produce and maintain the matrix
Why can’t you have thick amounts of cartilage?
Chondrocytes obtain their nutrition and O2 via diffusion
What sort of growth does cartilage have and why?
Interstitial growth
Chondrocytes continue secreting new matrix when embedded in the matrix, so internal expansion
Chondrocytes are capable of division within the matrix
What the four different layers of cartilage?
Superficial
Middle
Deep
Calcified (closest to the bone)
In hyaline/ articular cartilage, what portion of dry weight is type II cartilage?
50%
What are the two parts hyaline cartilage is made up from?
- 3D latticework of type II collagen
- Hydrated gel
How does the latticework of collagen fibres differ throughout the layers of cartilage?
Superficial/ middle are more horizontal orientated
Deep are more vertical
Deeper fibres (interfaced with bone) calcify
What is the structure of the hydrated gel?
Chondrocytes
No blood vessels
No lymphatics
No nerves
Deeper portion calcifies
What is Aggroglycan
The major glycoprotein in the articular cartilage
What does Aggrecan do?
Contributes to water retention and provides resistance to compression
How does aggregan help with load bearing
Proteoglycan aggregates are depicted as being entrapped by collagen fibrils. In the relaxed state the aggregates swell as the anionic chondroitin sulfate and keratan sulfate chains draw water into the tissue until an equilibrium is attained in which swelling is balance by tensile forces in the collagen fibrils. Under compression, water is displaced and the chondroitin sulfate and keratan sulfate chains are brought into closer proximity, so increasing their swelling potential and balancing the applied load. The increased swelling potential is dissipated upon removal of the load as the original equilibrium is restored.
Pitcture on one note
What happens when cartilage is compressed
Negatively charged sites of aggrecan are pushed closer together, which increases their repulsive force, so cartilage becomes stiffer
As volume of cartilage has decreased due to compression, water flows out
Why do the prteoglycans spread out an occupy a large space
They have negative charges from sulfate groups and carboxylate groups
What happens when cartilage is decompressed
Water flows back into cartilage as volume increases
Aggregan molecules become further apart
