Fluid Shift & Pulmonary and Systemic Oedems

Question 1

What is the purpose of the interstitial fluid?

Answer 1

it acts as a go-between the blood and the body cells

Question 2

What is the purpose of the capillaries?

Answer 2

to allow rapid exchange of gases, water & solutes with interstitial fluid, they deliver nutrients and O2 to the cells and remove the metabolites

Question 3

What effects the blood flow in the capillaries?

Answer 3

The contractile state of the arterioles

Question 4

What vessels regulate regional blood flow to the capillary bed (CB) in most tissues?

Answer 4

Terminal arterioles

Question 5

What regulates flow in a few tissues such as the mesentery?

Answer 5

Precapillary Sphincters

Question 6

What speed does blood flow through the capillaries and why this speed?

Answer 6

It is very slow to allow adequate time of exchange with the interstitial fluid

Question 7

How doe exchangeable proteins move across the capillary wall?

Answer 7

Through vesicular transport

Question 8

What gradient does fluid movement follow?

Answer 8

The pressure gradient (Fick’s Law of Diffusion)

Question 9

How do lipid soluble substances move through the capillary wall?

Answer 9

Through the endothelial cells

Question 10

How do water soluble substances move through the capillary wall?

Answer 10

substances go through the water-filled pores

Question 11

How is transcapillary fluid flow driven?

Answer 11

by the pressure gradient across the capillary wall

Question 12

What is ultra-filtration?

Answer 12

exchange across the capillary wall of essentially protein-free plasma

Question 13

Net filtration pressure (NFP) is directly proportional to

Answer 13

Forces favouring filtration - Forces opposing filtration

Question 14

What coefficient affects net fluid filtration?

Answer 14

Filtration coefficient Kf

Question 15

What are the 2 forces which favour filtration in transcapillary flow?

Answer 15

Pc - capillary hydrostatic pressure

- interstitial fluid osmotic pressure

Question 16

What are the 2 forces which oppose filtration in transcapillary flow?

Answer 16

• capillary osmotic pressure

Pi - interstitial fluid hydrostatic pressure (-ve in some tissues)

Question 17

What are the names of the forces which determine transcapillary fluid flow?

Answer 17

Starling forces

Question 18

What movement of fluid do starling forces favour?

Answer 18

They favour filtration at the arteriolar end of the capillary bed and the venular end of the capillary bed

Question 19

What substance in the plasma generally cannot cross the capillary bed?

Answer 19

The plasma proteins

Question 20

NFP =

Answer 20

(Pc + interstitial fluid osmotic pressure) - (Pi + capillary osmotic pressure)

Question 21

By how much does the filtration of fluid exceed re absorption each day?

Answer 21

2-4 L this excess is returned to circulation in the lymphatics

Question 22

What is the definition of oedema (edema)?

Answer 22

accumulation of fluid in interstitial space

Question 23

What are the causes of oedema?

Answer 23

• raised capillary pressure
• reduced plasma osmotic pressure
• lymphatic insufficiency
• changes in capillary permeability

Question 24

What raises capillary pressure?

Answer 24

• arteriolar dilation
• raised venous pressure possibly due to (LV failure - pulmonary oedema, RV failure - peripheral oedema (ankle, sacral) and prolonged standing

Question 25

What is the resistance in the pulmonary capillaries?

Answer 25

The pulmonary capillary hydrostatic pressure is low, the osmotic

Question 26

What causes a reduced osmotic pressure?

Answer 26

• malnutrition
• protein malabsorption
• excessive renal excretion of protein
• hepatic failure
  (reduced plasma proteins)

Question 27

What causes lymphatic insufficiency?

Answer 27

Lymph node damage

filariasis - elephantiasis

Question 28

What causes changes in capillary permeability?

Answer 28

inflammation

histamine increases leakage of proteins

Question 29

What can left ventricular failure result in?

Answer 29

Pulmonary oedema as there is fluid accumulation in the interstitial and intraalveolar lung spaces

Question 30

How does pulmonary oedema manifest clinically?

Answer 30

varying degrees of shortness of breath

crepitations in the lung bases

Question 31

What is seen through pitting oedema?

Answer 31

Oedema is caused by the increased hydrostatic pressure sign of heart failure rather than lymphatic problem