Physiology: joints

Question 1

what are the different types of joints

Answer 1

synovial, fibrous and cartilaginous

Question 2

briefly describe a fibrous joint(synarthrosis) and give an example

Answer 2

bones united by fibrous tissue

example = between bones of skull in adults

Question 3

what movement do fibrous joints allow

Answer 3

no movement

Question 4

briefly describe a cartilaginous joint(amphiarthrosis) and give an example

Answer 4

bones united by cartilage

example = intervertebral discs

Question 5

briefly describe a synovial joint(diarthrosis) and give an example

Answer 5

bones separated by a cavity and united by a fibrous capsule, and extra-articular structures
example = knee joint

Question 6

what does the cavity in synovial joints contain

Answer 6

synovial fluid

Question 7

describe what the synovial membrane is, and where it is found

Answer 7

vascular connective tissue with capillaries and lymphatics, found in inner aspect of fibrous capsule

Question 8

describe the function of the synovial membrane

Answer 8

contains synovial cells(fibroblasts) that produce synovial fluid

Question 9

what are the articular surfaces of bones covered with in synovial joints

Answer 9

articular(hyaline) cartilage

Question 10

what different types can synovial joints be classified into

Answer 10

simple = one pair of articular surfaces
compound = more than one pair of articular surfaces

Question 11

what extra-articular structures are synovial joints supported by

Answer 11

bursa, ligaments, tendons

Question 12

what are the physiological functions of joints

Answer 12

structural support and purposeful motion

Question 13

describe the roles of joints in purposeful motion

Answer 13

stress distribution, confer stability, joint lubrication

Question 14

what is joint lubrication provided by

Answer 14

synovium-derived hyaluronic acid, synovium-derived lubricin and cartilage interstitial fluid

Question 15

describe the functions of synovial fluid

Answer 15

lubricates joint, facilitates movement, helps minimise wear-and-tear, nutrition of articular cartilage

Question 16

what are chondrocytes

Answer 16

cartilage cells

Question 17

what does synovial fluid supply chondrocytes with and remove

Answer 17

supplies with O2 and nutrients

removes CO2 and waste products

Question 18

describe how synovial fluid is replenished and absorbed

Answer 18

continuously replenished and absorbed by the synovial membrane, not a static pool

Question 19

describe the normal viscosity and appearance of synovial fluid

Answer 19

high viscosity, colourless and transparent

Question 20

describe how synovial fluid and viscosity are affected by joint movement

Answer 20

rapid joint movement associated with decreased viscosity and increased elasticity

Question 21

describe the viscosity and appearance of synovial fluid in inflammation

Answer 21

low viscosity, straw-yellow colour and translucent

Question 22

describe the viscosity and appearance of synovial fluid in septic synovial fluid

Answer 22

variable viscosity and colour, opaque

Question 23

describe how number of WBCs and leucocytes varies between normal, inflammatory and septic synovial fluid

Answer 23

normal < inflammatory < septic

Question 24

what are the main functions of articular cartilage

Answer 24

provides a low friction lubricated gliding surface, reducing wear-and-tear, and distributes the contact pressure to the subchondral bone

Question 25

what type of cartilage is articular cartilage usually

Answer 25

hyaline

Question 26

briefly describe the properties of articular cartilage

Answer 26

elastic and sponge-like

Question 27

what is the special extracellular matrix(ECM) of articular cartilage made up of

Answer 27

water(70%), collagen(20%) and proteoglycans(10%)

Question 28

describe the function of chondrocytes

Answer 28

synthesise, organise and degrade the ECM of articular cartilage

Question 29

describe the ECM turnover in normal joints

Answer 29

the rate of degradation doesn’t exceed the rate at which it is replaced(synthesised)

Question 30

describe how and what catabolic factors can affect articular cartilage ECM turnover

Answer 30

TNF-alpha and IL-1

stimulate proteolytic enzymes and inhibit proteoglycan synthesis

Question 31

describe how and what anabolic factors can affect articular cartilage ECM turnover

Answer 31

TGF-beta and IGF-1

stimulate proteoglycan synthesis and counteract effects of IL-1

Question 32

describe the effects on the subchondral bone if the cartilage is worn down

Answer 32

osteophyte formation, sclerosis in subchondral bone, cyst formation

Question 33

describe the effect on the synovium in rheumatoid arthritis

Answer 33

synovial proliferation and inflammation

Question 34

describe the effect of gout or pseudogout on a joint

Answer 34

deposition of crystals(e.g. uric acid)