Oedema

Question 1

Another name for capillary beds

Answer 1

microcirculation

Question 2

What is the input into capillaries?

Answer 2

arteriole blood

Question 3

What kind of blood flow is travelling through the arterioles?

Answer 3

smooth flow

Question 4

How is the blood flow controlled to go to specific capillaries from the arterioles?

Answer 4

arterioles have pre-capillary sphincter

smooth muscle which can be contracted and relaxed, which opens or closes the capillary beds

Question 5

How do venules control where blood goes from the capillaries?

Answer 5

post-capillary sphincter

smooth muscle which can be contracted and relaxed, makes it harder or easier for blood to travel through that venule

Question 6

Function of capillaries

Answer 6

sites of exchange

Question 7

Can capillaries control where the blood flows to?

Answer 7

no - have no smooth muscle in their walls

Question 8

What is the blood flow velocity in capillaries like?

And what does it depend on?

Answer 8

not constant - can vary from 0 to 8mm/s

depends on contractile state of the arterioles/pre-capillary vessels

Question 9

What is the solute/solvent movement across capillaries like?

And what does it depend on?

Answer 9

not constant

depends on the permeability which can vary between tissues, at different times and along the capillary bed

Question 10

What is solute/solvent movement across capillaries dricen by?

Answer 10

diffusion - largely
filtration - fluid, find space
pinocytosis - larger molecules, lipid insoluble packed into vesicles

Question 11

What are the prime determinants for diffusion?

Answer 11

Capillary permeability of substance and surface area

Question 12

What is the law associated with the rate of diffusion?

Answer 12

Fick’s Law

Question 13

What type of substances readily pass through endothelial cells?

Answer 13

lipid soluble substances

eg. O2 and CO2

Question 14

How does fluid move?

Answer 14

filtration and reabsorption

Question 15

What is filtration and reabsorption?

Answer 15

bulk flow

movement of a volume of protein-free fluid out of the capillary (filtration) and back (reabsorption)

Question 16

Why is bulk flow important?

Answer 16

helps to determine distribution of ECF

Question 17

Driving forces for filtration

Answer 17

capillary hydrostatic pressure (Pc)

interstitial fluid colloid osmotic pressure (πi)

Question 18

Driving forces for reabsorption

Answer 18

capillary (plasma) colloid osmotic pressure (πc)

interstitial fluid hydrostatic pressure (Pi)

Question 19

What is capillary hydrostatic pressure (Pc) a major determinant of?

Answer 19

fluid movement

Question 20

What does capillary hydrostatic pressure depend on?

and give an example

Answer 20

pre/post capillary resistances due to:
venous pressure
(arterial pressure)

Question 21

If arteriole constricts, how does Pc change?

Answer 21

increased pressure upstream
decreased pressure downstream
therefore increased resistance and precapillary constriction reduces Pc

Question 22

If venule constricts, how does Pc change?

Answer 22

increased pressure upstream
decreased pressure downstream , less flow
postcapillary constriction increases Pc

Question 23

How important is interstitial fluid colloid osmotic pressure on fluid movement?

Answer 23

minor determinant

Question 24

What does interstitial fluid colloid osmotic pressure depend on ?

Answer 24

presence of protein in interstitium, therefore the capillary premeability to protein which is normally very low

Question 25

How important is capillary colloid osmotic pressure on fluid movement? and why?

Answer 25

major determinant | lots of protein in the blood

Question 26

What does capillary colloid osmotic pressure depend on ?

Answer 26

synthesis/breakdown of protein - liver capillary permeability to protein abnormal protein loss - kidney damage

Question 27

Symptoms of end-stage liver failure

Answer 27

lose fluid to tissues and abdomen hear water sloshing in abdominal cavity lost protein in blood, decreased colloid osmotic pressure

Question 28

How important is interstitial fluid hydrostatic pressure on fluid movement?

Answer 28

minor determinant

Question 29

What does interstitial fluid hydrostatic pressure depend on?

Answer 29

interstitial fluid volume compliance of organ effective drainage

Question 30

What provides drainage for the cappilaries?

Answer 30

lymphatic system

Question 31

Characteristics of lymphatic system which allows for drainage

Answer 31

valved and highly permeable to protein

Question 32

What is the purpose of the lymphatic system?

Answer 32

returns excess filtered fluid and 95% of protein lost from vascular system back into circulation close to jugular vein

Question 33

What occurs if the lymphatic system does not function?

Answer 33

build up of fluid in tissues | swelling

Question 34

Equation for fluid movement

Answer 34

fluid movement ∝ filtration forces - reabsorption forces ``` Q ∝ (Pc + πi) - (πc + Pi) Q = Kf [(Pc + πi) - (πc + Pi)] where Kf (filtration coefficient) is a constant that depends on permeability and surface area available ```

Question 35

What does capillary fluid transfer depend on and why?

Answer 35

capillary hydrostatic pressure plasma colloid osmotic pressure πi and Pi are normally negligble

Question 36

If capillary hydrostatic pressure is increased, how does this affect fluid movement?

Answer 36

increased filtration

Question 37

If plasma colloid osmotic pressure is increased, how does this affect fluid movement?

Answer 37

increased reabsorption

Question 38

If Pc > πc, what occurs?

Answer 38

net filtration

Question 39

If Pc < πc, what occurs?

Answer 39

net reabsorption

Question 40

How does Pc and πc present in a typical capillary?

Answer 40

higher Pc pressure on arteriolar side same pressures mid-capillary higher πc pressure on venular side

Question 41

How does Pc and πc change moving from arteriole to venules? and what does this mean for the net movement of fluid?

Answer 41

Pc decreases πc remains constant net filtration until Pc = πc, then no movement net reabsorption once Pc < πc

Question 42

How would Pc and πc be affected by pre-capillary vasoconstriction? and therefore movement of fluid? give an example of where this occurs

Answer 42

reduced Pc, no change in πc therefore less time for filtration and therefore increased reabsorption eg. lungs - not driving fluid into alveoli and do not interfere with gas exchange

Question 43

How would Pc and πc be affected by pre-capillary vasoconstriction? and therefore movement of fluid? why might this occur?

Answer 43

increase Pc due to increased venous pressure no change in πc increased filtration RHS heart failure - swollen ankles LHS - breathlessness due to increased hydrostatic pressure in pulmonary veins

Question 44

How would Pc and πc be affected by hypoproteinaemia? | Examples of when this would occur

Answer 44

πc reduced, no change in Pc reduction in net reabsorption, increased filtration, liver failure - comprimised capacity for protein synthesis renal failure - lose protein in urine

Question 45

Causes of oedema

Answer 45

lymphatic obstruction - reduced drainage increased venous pressure - congestion (HF) hypoproteinaemia - renal damage hypervolaemia inflammation - vasodilation and increased permeability