Fluid shifts across the capillary wall: pulmonary & systemic oedema

Question 1

what percentage of body weight does total body water occupy in a young man?

Answer 1

60% of body weight

Question 2

what fraction of body water is extra-cellular and what percentage of this is interstitial?

Answer 2

1/3rd of body water is extra-cellular

75%

Question 3

what does the interstitial fluid act as?

Answer 3

as the go between blood and body cells

Question 4

what are capillaries composed of?

Answer 4

= single layer of endothelial cells

Question 5

What is the function of the capillaries?

Answer 5

= allows rapid exchange of gases, water & solutes with interstitial fluid

Consequently;
= delivering nutrients & O2 to cells
&
= removes metabolites from cells

Question 6

what does blood flow in capillaries depend on?

Answer 6

depends on contractile state of arterioles

Question 7

what do terminal arterioles regulate?

Answer 7

regulate regional blood flow to capillary beds (CB) in most tissues

Question 8

what other thing regulates flow in few tissues (e.g. mesentery)

Answer 8

pre-capillary sphincters

Question 9

describe the flow of blood in capillary beds?

Answer 9

blood flows slowly to allow adequate time for exchange

Question 10

what do capillaries form when they unite?

Answer 10

venules

Question 11

how are exchangeable proteins moved across the capillary wall?

Answer 11

by vesicular transport

Question 12

what does fluid movement follow?

Answer 12

follows pressure gradient (bulk flow)

Question 13

what do the movement of gases and solutes follow?

Answer 13

follows Fick’s Law of diffusion (i.e. downhill)

Question 14

where do lipid soluble (lipophilic) substances go?

Answer 14

go through the endothelial cells

Question 15

where do water soluble (hydrophilic) substances go?

Answer 15

go through the water field pores

Question 16

Yes of No.

Can large molecules (e.g. plasma proteins) cross the capillary wall)?

Answer 16

No they CANNOT cross the wall

Question 17

what is trans-capillary fluid flow driven by?

Answer 17

PASSIVELY driven by pressure gradients across capillary wall. (ultra-filtration)

Question 18

what is ultra-filtration?

Answer 18

exchange across capillary wall of essentially protein free plasma

Question 19

What is the relationship between net filtration pressure =?

Answer 19

NFP = Forces favouring Filtration - Forces Opposing Filtration

Question 20

what also affects net fluid filtration?

Answer 20

= filtration co-efficient (Kf)

Question 21

what forces are involved in trans-capillary fluid flow?

Answer 21

starling forces

Question 22

what force FAVOURING FILTRATION n in trans-capillary fluid flow?

Answer 22

capillary hydrostatic pressure (MAIN) = Pc
and
interstitial fluid osmotic pressure

Question 23

what force OPPOSE FILTRATION?

Answer 23

capillary osmotic pressure (main)
and
interstitial fluid hydrostatic pressure = Pi

Question 24

describe the relationship between NFP, Pc, Pi and Pii and PiC?

Answer 24

NFP = (PC + Pii) - (Pic + Pi)

Question 25

where does starling force favour filtration and re-absoprtion?

Answer 25

Favours filtration = at arteriolar end

Favours re-absoprtion = at venular

Question 26

during a day, how does filtration exceed re-absoprtion?

Answer 26

filtration exceeds re-absoprtion by 2-4litres

Question 27

how is excess fluid is returned to circulation?

Answer 27

via lymphatics as lymph

Question 28

how much does pulmonary resistance comprise of the systemic circulation?

Answer 28

only 10%

Question 29

Is pulmonary capillary hydrostatic pressure low?

Answer 29

YES (8-11mmHg)

Question 30

what is capillary osmotic pressure?

Answer 30

25mmHg

Question 31

what does efficient lymphatic drainage remove?

Answer 31

removes any filtered fluid thus preventing accumulation of interstitial fluid

Question 32

what is oedema?

Answer 32

accumulation of fluid in interstitial space

Question 33

in pulmonary oedema, describe the effect of diffusion and gas exchange in the lungs?

Answer 33

1) diffusion distance increases

2) gas exchange compromised

Question 34

what are 4 cause of oedema?

Answer 34

1) raised capillary pressure
2) reduced plasma osmotic pressure
3) lymphatic insufficiency
4) changes in capillary permeability

Question 35

what 2 things cause raised capillary pressure?

Answer 35

1) arteriolar dilation

2) raised venous pressure
- left ventricular failure = pulmonary oedema

• right ventricular failure = peripheral oedema (ankle, sacral)
• prolonged standing = swollen ankles

Question 36

describe the plasma osmotic pressure in normal people and oedema patients?

Answer 36

Normal = 65-80g/l

Oedema if < 30g/l 
= malnutrition 
= protein malabsorption
= excessive renal excretion of protein 
= hepatic failure

Question 37

what 2 things cause lymphatic insufficiency?

Answer 37

1) lymph node damage

2) filariasis = elephantiasis

Question 38

what 2 things cause changes in capillary permeability?

Answer 38

1) inflammation

2) histamine increases leakage of protein

Question 39

where in particular does fluid accumulate in pulmonary oedema?

Answer 39

1) interstitial

2) intra-alveolar lung spaces

Question 40

what is a symptoms of pulmonary of pulmonary oedema?

Answer 40

shortness of breath

Question 41

in pulmonary oedema, what might you find clinically?

Answer 41

= crepitations in auscultation of lung bases

Question 42

in pulmonary oedema, what might a chest X-ray show?

Answer 42

= haziness in perihilar region

Question 43

where might you find pitting oedema?

Answer 43

1) ankles

2) sacrum