Pathology- Oedema

Question 1

what is the role of interstitial fluid

Answer 1

acts as a go between blood and body cells

Question 2

what does blood flow in the capillaries depend on

Answer 2

the contractile state of the arterioles

Question 3

describe the structure of capillaries and their purpose

Answer 3

single layer if endothelial cells- allow rapid exchange of gases, water and solutes with interstitial fluid

-delivery of oxygen and nutrients and removal of metabolites

Question 4

other than terminal arterioles what regulates blood flow in the capillary bed

Answer 4

precapillary sphincters, smooth muscle

Question 5

why is blood flow in the capillaries slow

Answer 5

to allow adequate time for exchange

Question 6

what do capillaries unite to form

Answer 6

venules

Question 7

what substances are able to pass through the endothelial cells in a capillary wall

Answer 7

lipid-soluble substances (O2, CO2)

Question 8

what substances pass through the pores of a capillary wall

Answer 8

small, water soluble substances (e.g Na+, K+, glucose, amino acids)

Question 9

what substances are moved through the capillary wall by vesicular transport

Answer 9

exchangeable proteins

Question 10

what substance cannot generally pass through the capillary wall

Answer 10

plasma proteins (large molecules)

Question 11

what law does the movement of gases and solutes follow

Answer 11

ficks law of diffusion
‘blood flow is proportional to the difference in concentration of a substance in the blood as it enters and leaves an organ’

Question 12

what drives trans-capillary fluid

Answer 12

pressure gradients across the capillary wall

Question 13

describe what is meant by transcapillary fluid being ‘ultra-filtration’

Answer 13

it is the exchange across the capillary wall of essentially protein free plasma

Question 14

what is net filtration pressure (NFP) inversely proportional to

Answer 14

forces favouring filtration - forces opposing filtration

Question 15

what does a filtration coefficient show? (Kf)

Answer 15

how easily permeable a membrane is to fluid

Question 16

what are the two forces favouring filtration (which is the most important)

Answer 16

Pc- capillary hydrostatic pressure (MVP)
PieI(i)- interstitial fluid osmotic pressure

(when these pressure rise they force fluid out of the capillaries)

Question 17

what is capillary hydrostatic pressure a result of

Answer 17

blood pressure

Question 18

what are the two forces opposing filtration and which is the most important

Answer 18

PieC- capillary osmotic pressure (MVP)

Pi- interstitial fluid hydrostatic pressure

Question 19

what is the difference between hyrdostatic and osmotic pressure

Answer 19

hydrostatic (pushing fluid out)

osmotic (pulling fluid in)

Question 20

what is usually the capillary osmotic pressure and why is it important

Answer 20

25mmHg, important due to plasma protein

Question 21

how do you calculate net filtration pressure

Answer 21

(capillary hydro static pressure + interstitial fluid osmotic pressure) - (capillary osmotic pressure + interstitial fluid hydro static pressure)

Question 22

describe the net filtration pressures in arteriolar end and venular end

Answer 22

arteriolar end positive (10mmHg)

venular end negative (favouring absorption of fluid into vessels)

Question 23

what happens to the capillary hydrostatic pressure as you go from arterioles to venules

Answer 23

decreases

Question 24

which exceeds the other during a day; filtration or re-absorption

Answer 24

filtration (by 2-4 litres)

Question 25

what happens to excess fluid

Answer 25

returns to circulation via the lymphatics as lymph

Question 26

what are the starling forces

Answer 26

osmotic and hydrostatic pressures

Question 27

is pulmonary resistance high or low

Answer 27

low

Question 28

is pulmonary capillary hydrostatic pressure low or high

Answer 28

low (8- 11mmHg)

Question 29

is pulmonary capillary osmotic pressure low or high

Answer 29

high (25mmHg)

Question 30

what prevents the accumulation of interstitial fluid (oedema)

Answer 30

efficient lymphatic drainage removes any filtered fluid low pressure of pulmonary capillaries allowing absorption of water

Question 31

what is oedmea

Answer 31

accumulation of fluid in interstitial and intraalveolar lung spaces

Question 32

what happens to gas exchange in pulmonary oedema

Answer 32

compromised as diffusion distance increases

Question 33

what are the causes of oedema

Answer 33

raised capillary pressure, reduced plasma osmotic pressure, lymphatic insufficiency, change in capillary permeability,

Question 34

what can cause raised capillary pressure

Answer 34

arteriolar dilatation, | raised venous pressure

Question 35

what can cause raised venous pressure

Answer 35

left ventricular failure, right ventricular failure, prolonged standing

Question 36

how does raised venous pressure affect pulmonary capillaries

Answer 36

back pressure in pulmonary capillaries

Question 37

what type of oedema does left ventricular failure cause

Answer 37

pulmonary oedema

Question 38

what type of oedema does right ventricular failure cause

Answer 38

peripheral oedema (ankle, sacral)

Question 39

what type of oedema does prolonged standing cause

Answer 39

peripheral- swollen ankles

Question 40

how does heart failure affect the frank-starling curve

Answer 40

shifts it to the right

Question 41

what causes reduced plasma osmotic pressure

Answer 41

malnutrition, protein malabsorption, excessive renal excretion of protein, hepatic failure

Question 42

what causes lymphatic insufficiency

Answer 42

lymph node damage, filariasis (parasitic worms) (a.k.a elephantiasis)

Question 43

what causes changes in capillary permeability

Answer 43

inflammation, histamine increases leakage of protein

Question 44

how is pulmonary oedema manifested clinically

Answer 44

dyspnoea (difficulty breathing), orthopnoea (shortness of breath), pink frothy sputum, crepitations in auscultation of lung bases, haziness in peripheral region in CXR

Question 45

where does pitting oedema occur

Answer 45

ankles, sacrum

Question 46

what usually causes pitting oedema

Answer 46

right sided heart failure