Articular Cartilage & Synovial Fluid Flashcards
what are synoviocytes? - what do they produce?
what are the two types?
which is more?
how do the synoviocytes sit on subintima?
The synovial intimal cells, termed synoviocytes, are believed to be responsible for the production of synovial fluid components, for absorption from the joint cavity, and for blood/synovial fluid exchanges,
1-3 cell layer
•Type A: bone marrow derived macrophage for immune surveillance
•Type B: fibroblast-like connective tissue cell for proteoglycan production - more than type A
no barrier between synoviocytes & subintima !! - no basement membrane = no barrier for fluid movement !!!
what is subintima of synovial membrane / synovium characterised by?
a) type of CT?
b) capillaries?
what is subintima of synovial membrane / synovium characterised by?
a) type of CT: loose CT - type II collagen
b) capillaries: high capillary network - fenestrated capillaries (have basement membrane
esssentially, what is synovial fluid? [2]
synovial fluid:
ultrafiltrate of blood [1] with added hyaluronic acid [1]
which cells make hyaluronic acid for synovial fluid? [1]
which cells make hyaluronic acid for synovial fluid? [1]
type B synoviocytes
normal synovial fluid is WHAT? [1]
what does this mean regarding synovial fluid analysis [1]
normal synovial fluid is acellular
what does this mean regarding synovial fluid analysis [1]
if extract - should be able to read text behind, because it should just be fluid
what is hemarthrosis?
when tear / rupture fenestrated capillaries -> goes into synovial fluid bc theres no BM
which two components of synovial fluid interact to make glycoproteic gel of SF? [2]
interaction between hyaluronic acid & albumin: creates a tangled mesh that causes the glycoproteic gel - increases the viscosity
what is basic overview of RA?
- synovial membrane proliferates - gets thicker - 20/40 cell layers thick. subintima infiltrated with lympocytes
- synovial fluid has less protein
- *- HA damaged**
- together: causes SF to be less vicous
- white blood cell infiltration makes it cloudy from WHITE blood cells - lymphocytes
what does synovial fluid do? [1]
what does synovial fluid do? []
- coats the free spaces between articulating cartilage: keeps them sepearate!!!
- *Also seeps into articular cartilage at rest:** thickens the articular cartilage (like a sponge):
i) Slippery weight-bearing film which reduces friction between cartilage
ii) Distributes force across joint surfaces
iii) Forms reserve volume: when moving the joint, the SF is forced out & back into the joint
iv) Helps nourish articular cartilage
v) causes the HA and albumin to interact more and become my glycoproteic
describe hhow loading area / unloading area changes during movement / rest !!
as fluid part of SF moves into / out of the articular cartilage at rest / movement: what happens to the viscosity of the SF?
as fluid part of SF moves into / out of the articular cartilage at rest / movement: what happens to the viscosity of the SF? [1]
- *viscosity changes:** has non-newtonian flow characteristics:
- *i) at rest: gels**
ii) with movement: less viscous
what is structure of HA acid like?
•Repeated glucuronic acid and N-acetylglucosamine subunits
•0.2 to 10 million Daltons molecular weight
–Size & amount decreases with age
•Viscoelastic properties
•Powerful moisture binding - due to fact it is a GAG: draws in water !
how does the structure of SF respond to movement?
a) what is structure like at low / slow frequency movement?
b) what is structure like at high/ fast frequency movement?
how does SF respond to movement?
a) what is structure like at low / slow frequency movement: molecules align in direction of movement: energy dissipated as viscous flow
b) what is structure like at high/ fast frequency movement: entangled molecular network !! resists deformation & acts as shock absorbed
what is lubricin? [1]
what is structure like? [1]
function? [1]
lubricin: water soluble glycoprotein
structure: equal proportions of protein and oligosaccharides
function:
* *Forms thin superficial barrier [1]**
* *- Repels joint surfaces, preventing contact of articular surfaces [1]**
which cells produce lubricin? [2]
–Produced by chondrocytes and synoviocytes
what are the different domains of lubricin? [3] are they adhesive or repulsive? [3[
how does this contribue to overall role of lubricin?
- PEX-like domain: adhesive
- Lubricin / mucin-like domain: repulsive
- SMB-like domain: adhesive
sticks out into the joint surface and form boundary layer of protection. Lubricin / Mucin-like domain repels the opposite surface and pushes them apart!
what is articular cartilage vascularity and neuronal like? [2]
why is most of articular cartilage no more than 4mm thick around the body? [1]
what is articular cartilage vascularity and neuronal like? [2]
avascular
aneuronal
why is most of articular cartilage no more than 4mm thick around the body? [1]
- *deep AC can get nutrition from bone**
- *superficial AC can get nutrients from SF - nut needs to be thin to allow diffusion**
articular cartilage is what type of cart? [1]
what type of collagen fibres is it made from? [1]
•Hyaline cartilage
–Collagen type II (Fibres)
–Polysaccharide glycosaminoglycans (GAGs) usually covalently linked to protein forming very large proteoglycan aggregates (Aggrecan)
•chondrotin sulphate
•keratan sulphate
–GAGs and proteoglycans form hydrated gel-like: due to -ve charge, attracts water
–Allows diffusion of nutrients, metabolites and hormones between blood and cartilage cells
what is function of AC? [3]
–Elastic, resilient structure acts as a shock absorber protecting the underlying bone (bc bone is v brittle)
–Smooth, slippery and very low coefficient of friction
–Deeper layer merges with a calcified layer (tidemark) that attaches it to subchondral bone.
what is the deformability of AC in upper [1] and lower zone [1]?
- can squeeze first part of the upper peripheral zone: upper layers are deformable
- lower layer is incompressable due to chondrocytic arrangement
overall awareness: how does AC overall structure change throughout structure?
how do the chondrocytes change throughout the structure of AC?
superficial / middle / deep space?
tide mark?
deeper than tide mark?
superficial: small, flat and sparse
middle space: cells get bigger / hypertrophy. go into cell cycle and proliferate
deep space: hypertrophy again, become rounder - form column of cells !!
tide mark: calcification occurs
deeper than tide mark: death of chondrocytes, for osteoblasts moving iim
how do collagen fibres change through AC? [3]
superficial / middle / deep zone?
superficial: collagen fibres are parralel with the surface: smooth & strong !
middle zone: collagen fibres become oblique / criss cross - chondrocytes can fit into pockets
deep zone: collagen fibres perpindicular to surface to follow the stacks of chondrocytes. makes it incompressable
what is structure of gags and proteoglycans like in AC?
- Proteoglycans special class of glycoproteins heavily glycosylated
- Core protein with 1 or more covalently attached glycosaminoglycan chain
- Aggrecan major proteoglycan/GAG in cartilage
where do u find the gag / aggrecan complexes in AC? - next to what?
how does this interact with water and movement?
aggrecan complexes fit into the collagen type 2 criss cross in intermediate middle zone = water attracting unit with collagen holding aggrecan complexes into place
as squeeze AC - water can move out, but the aggrecan stays in place, so at rest the water moves back
ECM is made by what % of
a) water?
b) collagen?
c) proteoglycans?
•ECM
–Around 70-80% water
–Collagen 15% (predominantly type II)
•Network of fibrils that give overall framework and shape of the cartilage
•Makes pockets that are filled with water binding proteoglycans complexes – regulate compressibility
–Proteoglycans 15% have lots of negative charges that attract water
•Lacks blood and lymphatic vessels
–Survival and synthetic activity depend on diffusion of nutrients and metabolites through matrix
what happens to AC when u age?
Aggrecan amount and complexity changes with age:
- Old = smaller fewer side branches
- Gaps in the collagen pockets
•Fewer negative charges while water can move in and out there is less to hold it in place
what is OA caused by?
loss & degradation of AC: causes exposed bone due to loss of joint space !!
