Synoival fluid

Question 1

how much syvoial fluid do you have

Answer 1

• at most 5ml but usually 2ml

Question 2

what is the calcifying mark called

Answer 2

• Calcifying mark is called the tidemark can see how much the calcium has been precipitated onto the hyaline matrix

Question 3

describe the structure of the synovial membrane

Answer 3

• 1-3 cells thick
• made up of synoviocytes
• no basement membrane
• synoviocytes sit on the subitima
• no barrier for fluid movement

Question 4

what are the two types of synoviocytes

Answer 4

type A and type B

Question 5

describe type A synoviocyte

Answer 5

• Type A bone marrow derived macrophage -get rid of any foreign pathogen that gets into the synovial joint

Question 6

describe type B

synoviocyte

Answer 6

• Type B fibroblast-like connective tissue cell, there are more of these

Question 7

describe what the subinitma has in it

Answer 7

• contains a dense network of fenestrated capillaries

Question 8

what is synovial fluid made up of

Answer 8

• made up of the ultra filtrate of blood ( leaks out of the capillaries through the subitima and into the joint cavity)
• has hyaluronic acid added to it - this makes it thick and viscous

Question 9

what colour should the synovial fluid be

Answer 9

• When you take the synovial fluid sample and put it up against a text then you should be able to read through it – should be clear
• Can becomes yellow this is normal

Question 10

what happens when the synovial membrane tears

Answer 10

the synovial membrane can tear and this means that we now get red blood cells in the synovial fluid as the blood is able to gain access to the joint capsule and fill it
- Synovial flood is no longer see view and is cloudy

Question 11

what is the composition of the synovial fluid

Answer 11

•	pH - 7.38
•	WBCs - mainly phagocytes 
•	Hyaluronate
•	Glucose
•	Protein
–	albumin (%)		60
–	globulin (%)		40
•	(+ ions, lactate, etc)
•	Lubricin

Question 12

what is rheumatoid arthritis

Answer 12

• this is an autoimmune condition that attach synovial joints and membranes,
• attacks tendon sheaths
• attacks some serous membrane as well

Question 13

what happens in rheumatoid arthritis

Answer 13

• cell proliferate and get thicker - T lymphocytes and CD4 T helper cells
• Subintima also thickens and becomes more fibrotic – this produces differnet synovial fluid, the cytokines that are produced from this lymphocyte, this causes the blood vessels to become more leaky and means that cells can now enter the synovial fluid
• lots of neutrophils and other immune cells in the synovial fluid

Question 14

whats the difference in consistency of synovial fluid in rheumatoid arthritis versus oesothatrisi

Answer 14

• fluid is cloudy in RA whereas in OA colour is darkened but it is still lear

Question 15

how does synovial fluid distribute fluid

Answer 15

• At the loaded site it seeps in and as you put pressure on it the fluid comes out and forces the surfaces apart and stop them bashing into each other when you stand up, this forms a reserve volume, this redistributes the force across the surfaces
• In different parts of the joint fluid is forced out and in parts of the joint that are not under strain fluid moves back in, this is so it redistributes fluid to where it is needed
• The hyaluronic acid does not seek it and they become concentrated at the point where you are losing more of the fluid

Question 16

what is the largest joint in the body and how much synovial fluid does it have

Answer 16

• Knee joint = largest joint in body

– 1-2mls of synovial fluid

Question 17

what does synovial fluid do to articular cartilage

Answer 17

– Forms reserve volume in articular cartilage

– Helps nourish articular cartilage

Question 18

what is the articular cartilage and what does it do

Answer 18

– Slippery weight-bearing film which reduces friction between cartilage
– Distributes force across joint surfaces

Question 19

what is the biomechanics of the synovial fluid

Answer 19

• Non-Newtonian flow characteristics

Question 20

what is thixotropic viscosity

Answer 20

• this means that its viscosity is not constant
• – this means that it gels at rest this is partially of the seeping in of the fluid part into the articular capsule means that hylaurinc acid is left, this interacts with albumin, globumin and other strands of hyaluronic acid to form a tangled pass of hylaurinic acid, albumin and globulin
• at rest it gels, wit movement it is less viscous

Question 21

viscosity ….

Answer 21

decreases as you move

Question 22

what happens when you initiate movement

Answer 22

• When you initiate movement the tangled mass increases for a short period of time viscosity until the fluid goes back in and you continue to move

Question 23

what is forced from the articular cartilage when compressed

Answer 23

water is forced back into the synovial fluid

Question 24

what is hyaluronic acid made out of

Answer 24

• Repeated glucuronic acid and N-acetylglucosamine subunits

Question 25

what is hyaluronic acid

Answer 25

- Hyaluronate = glycosaminoglycan

Question 26

what varies with age with hyaluronic acid

Answer 26

- size and amount decreases with age

Question 27

what does the tangled mass of hyaluronic acid, albumin globulin do

Answer 27

- Act as a shock absorber - Acts to store energy – if you continue to move at a slower speed and slower frequency – they unwind and untangle themselves and energy is dissipated as viscous flow

Question 28

what is lubricin(PRG4)

Answer 28

- it is a water soluble glycoprotein that is secreted into the synovial joint – Equal proportions of protein and oligosaccharides

Question 29

What is lubricin produced by

Answer 29

- chondrocytes | - synoviocytes type B cells

Question 30

what does lubricin do

Answer 30

• Forms thin superficial barrier | – Repels joint surfaces, preventing contact of articular surfaces

Question 31

describe the structure of lubricin

Answer 31

• It has a C terminal end and an terminal end that are both adhesive the part in the middle is a mucin domain that holds water

Question 32

what is a characteristic of articular cartilage

Answer 32

- Articular cartilage is avascular and aneural – no blood vessel or nerve supply, therefore it struggles to get nutrients and needs a other source

Question 33

how does articular cartilage get its nutrients

Answer 33

- Synovial fluid brings in glucose and oxygen | - has a high oxygen tension, the oxygen gradient goes high to low and glucose goes high to low

Question 34

describe the structure of articular cartilage

Answer 34

- hyaline cartilage - made from collagen type II fibres - GAGs covalent. linked to proteins and form proteoglycans such as aggrecan, chondrotin sulphate, keratan sulphate - - GAGs and proteoglycans form hydrated gel-like - Allows diffusion of nutrients, metabolites and hormones between blood and cartilage cells

Question 35

what is the role of articular cartilage

Answer 35

– Elastic, resilient structure acts as a shock absorber protecting the underlying bone – Smooth, slippery and very low coefficient of friction – Deeper layer merges with a calcified layer (tidemark) that attaches it to subchondral bone.

Question 36

what are the articular cartilage layers

Answer 36

- superficial zone - middle zone - deep zone - then you have a tide mark - then calcified zone

Question 37

describe superficial zone

Answer 37

- They are small flattended cells - collagen fibres are oreintatioed horiztonal and parallel with the articular surface, chronodcytes fit in between the collagen fibres

Question 38

describe middle zone

Answer 38

- Bigger and more rounded - collage fibres take up a random oreination and forms pocket to which we can fit proteoglycans - proteoglycans are in the middle regions

Question 39

describe the deep zone

Answer 39

- Bigger and can know see the columns – they are stacked one on top of the other, mini version of the epipsypical growth plate but at a lower rate of proliferation - the collagen fibres are now orientated perpendicular to the surface, they run verticular either side of the chrondycte column – this is why these areas are not compressible

Question 40

what is the main proteoglycans in cartilage

Answer 40

aggrecan

Question 41

what are proteoglycans

Answer 41

- special class of glycoproteins that are heavily glycosylated - core protein with 1 or more covalent attached glycosaminoglycan chain

Question 42

describe the ECM of the articular capsule

Answer 42

* 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

Question 43

what makes the ECM of articular cartilage

Answer 43

- made by chondrocytes | - only around 1% are chondrocytes

Question 44

what happens when you get older to proteoglycans

Answer 44

• Less proteoglycans – less ability to let water in, bones basically dries out and cracks, and these cracks get bigger