Physiology 3

Question 1

how are synovial joints supported?

Answer 1

extra-articular structures

• ligaments
• tendons
• bursors

Question 2

give 2 functions of joints

Answer 2

structural support

purposeful movement

Question 3

give roles of joints in movement

Answer 3

distribute stress (often through muscles over joint)
confer stability via shape, ligaments and synovial fluid
joint lubrication
- cartilage interstitial fluid
- synovium derived hyaluronic acid
- synovium derived lubricin

Question 4

how does a joint confer stability?

Answer 4

shape of articular component
ligaments
synovial fluid (acts as adhesive seal that permits sliding motion)

Question 5

what are the functions of synovial fluid?

Answer 5

• lubricates joint
• facilitates movement by reducing friction
• minimises wear and tear via lubrication
• aids nutrition of articular cartilage
• supplies chondrocytes (cartilage cells) with O2 and nutrients and removes CO2 and waste products

Question 6

how much synovial fluid is in the knee?

Answer 6

<3.5 ml

Question 7

is synovial fluid static?

Answer 7

no

continuously replenished by synovial membrane

Question 8

is synovial fluid thin or viscous?

Answer 8

viscous

due to presence of hyaluronic acid (mucin) produced by synovial cells

Question 9

is synovial fluid always the same?

Answer 9

no
viscosity and elasticity varies with joint movement
rapid movement = decreased viscosity and increased elasticity

Question 10

where are constituents of synovial fluid derived from?

Answer 10

dialysis of blood plasma

Question 11

how many cells are contained within synovial fluid?

Answer 11

only a few

mainly mononuclear leucocytes

Question 12

what changes occur in synovial fluid in osteoarthritis?

Answer 12

the ability of synovial fluid to change viscosity and elasticity is defective

Question 13

what does synovial fluid look like?

Answer 13

clear and colourless

high viscosity

Question 14

what is the cell count of synovial fluid?

Answer 14

<200/mm3 WBC
- polymorphs make up <25/mm3
WBC count will increase in inflammatory and septic arthritis

Question 15

when can synovial fluid be red?

Answer 15

traumatic synovial tap

haemorrhagic arthritis

Question 16

how does clarity/colour of synovial fluid change in septic arthritis?

Answer 16

becomes opaque due to high number of WBCs
variable colour
less viscous

Question 17

what does articular cartilage do?

Answer 17

mainly prevents wear and tear of joints by providing low friction, lubricated gliding surface
distributes pressure to bone

Question 18

what determines the mechanical properties of articular cartilage?

Answer 18

determined by composition of ECM and interaction between solid and fluid phase of cartilage

Question 19

what are the zones of articular cartilage?

Answer 19

superficial
middle (biggest)
deep
calcified

Question 20

how do zones of articular cartilage differ?

Answer 20

organization of collagen fibres and relative content of cartilage components

Question 21

what type of cartilage is articular cartilage?

Answer 21

hyaline

Question 22

what properties of articular cartilage have?

Answer 22

elastic

sponge-like

Question 23

what are the components of articular cartilage?

Answer 23

special ECM made of water, collagen (mostly type 2) and proteoglycans

Question 24

what is the function of water in cartilage?

Answer 24

maintains resiliency of tissue and contributes to nutrition and lubrication
70% of cartilage net weight (unevenly distributed)

Question 25

what is the function of collagen in cartilage?

Answer 25

provides tensile strength and stiffness and maintains architecture 20% of cartilage net weight (mainly type 2)

Question 26

what is the function of proteoglycans in cartilage?

Answer 26

compressive properties associated with weight bearing | 10% of cartilage weight

Question 27

what are proteoglycans composed of and where are they found?

Answer 27

glycosaminoglycan | highest concentration in middle and deep zone of cartilage

Question 28

what happens to cartilage components with age?

Answer 28

they all decrease with age

Question 29

what makes up most of the total cartilage volume in the body?

Answer 29

ECM (98%)

Question 30

what maintains the ECM?

Answer 30

chondrocytes | they synthesise, organise and degrade

Question 31

how do articular cartilage cells receive nutrients and O2?

Answer 31

articular cartilage is avascular so they get nutrients from synovial fluid

Question 32

how do the rates of ECM degradation and synthesis match up?

Answer 32

degradation never exceeds synthesis

Question 33

how do chondrocytes break down ECM components?

Answer 33

metalloproteinse proteolytic enzymes - collagenase - stromelysin

Question 34

how does ageing affect articular cartilage?

Answer 34

changes in relative amounts of the 3 components of cartilage changes the mechanical properties of the cartilage

Question 35

how might ECM cause joint disease?

Answer 35

if rate of ECM degredation exceeds synthesis rate

Question 36

what are the catabolic factors of cartilage matrix turnover and what do they do?

Answer 36

TNF alpha, IL-1 | stimulate proteolytic enzymes and inhibit proteoglycan synthesis

Question 37

what are the anabolic factors of cartilage matrix turnover and what do they do?

Answer 37

TGF beta and IGF 1 | stimulate proteoglycan synthesis and counteract effects of IL1

Question 38

what are the markers of cartilage degredation?

Answer 38

serum and synovial keratin sulphate - increase = cartilage breakdown type 2 collagen in synovial fluid - increase = cartilage breakdown

Question 39

give 4 examples of problems that can arise in a joint?

Answer 39

osteoarthritis - cartilage and synovial composition deteriorate rheumatoid arthritis - synovial cell proliferation and inflammation cause rheumatoid arthritis

Question 40

what causes rheumatoid arthritis?

Answer 40

synovial cell proliferation and inflammation cause rheumatoid arthritis

Question 41

what causes gouty arthritis?

Answer 41

deposition of salt crystals (e.g uric acid)

Question 42

what causes tendonitis?

Answer 42

injury and inflammation to periarticular structures causing soft tissue rheumatism - injury to the tendon

Question 43

3 changes in subchondral bone in osteoarthritis?

Answer 43

cyst formation osteophyte formation sclerosis

Question 44

what are the 3 types of joint?

Answer 44

synovial fibrous cartilaginous

Question 45

describe fibrous joints

Answer 45

``` syanthrosis unites bone (e.g skull sutures) doesn't allow any movement ```

Question 46

describe cartilaginous joints

Answer 46

AKA amphiarthrosis bones united by cartilage allows limited movement e.g - IV discs, pubic symphysis

Question 47

what are synovial joints?

Answer 47

diarthrosis bones separated by a cavity containing synovial fluid and united by a fibrous capsule as well as extra-articular structures

Question 48

what lines the inner aspect of fibrous capsule of synovial joints?

Answer 48

synovial membrane | - vascular connective tissue with capillary networks and lymphatics

Question 49

what is the function of the synovial membrane?

Answer 49

contains synovial cells which produce synovial fluid

Question 50

what covers the articular surfaces?

Answer 50

hyaline cartilage

Question 51

what are the 2 types of synovial joint?

Answer 51

simple (one pair of articular surfaces) | compound (more than one pair of articular surfaces - eg. elbow)