Fluid Shift across the capillary wall

Question 1

What percentage of the body water is extra cellular fluid? and what percentage of this is interstitial?

Answer 1

1. 1/3

2. 75%

Question 2

What does interstitial fluid act as?

Answer 2

a go between blood and body cells

Question 3

What is the function of the capillaries?

Answer 3

Allow rapid exchange of gases, water & solutes with Interstitial Fluid
Delivery of nutrients and O2 to the cells
Removal of metabolites from cells
Blood flow in the capillaries depends on the contractile state of the arterioles

Question 4

What is the function of the terminal arterioles?

Answer 4

regulate regional blood flow to the Capillary Bed in most tissues

Question 5

What other thing regulates regional blood flow - apart from the terminal arterioles?

Answer 5

Precapillary Sphincters

Question 6

How are exchangable proteins moved across the capilary wall?

Answer 6

vesicular transport

Question 7

How are lipid soluble substances moved across the capilary wall?

Answer 7

endothelial cells

Question 8

How do water soluble substances move across the capilary wall?

Answer 8

water filled pores

Question 9

Which molecules usually cannot cross the capillary wall?

Answer 9

large substances

Question 10

What Law does the movement of gases and solutes follow?

Answer 10

Ficks law of diffusion

Question 11

What is transcapillary flow driven by?

Answer 11

passively driven by pressure gradients across the capillary wall
(Ultra-filtration)

Question 12

What is Ultra-filtration?

Answer 12

exchange across the capillary wall of essentially protein-free plasma

Question 13

What does Net Filtration Pressure =

Answer 13

(NFP) = Forcesfavouring filtration - Forces opposing filtration

Question 14

What is the name of the forces involved in trascapillary flow?

Answer 14

Starling Forces

Question 15

Do the arterioles or venules have a higher pressure?

Answer 15

ARTERIOLES

Question 16

What are the forces favouring filtration in transcapillary fluid flow?

Answer 16

Capillary hydrostatic pressure (main)

Interstitial fluid osmotic pressure

Question 17

What are the forces opposing filtration in transcapillary fluid flow?

Answer 17

Capillary Osmotic Pressure (main)

Interstitial fluid hydrostatic pressure

Question 18

What do Starling forces favour?

Answer 18

Filtration at arteriole end

Reabsorption at venular end

Question 19

How is excess fluid returned to the circulation? What does this prevent?

Answer 19

via the lymphatics as lymph

build up of interstitial fluid

Question 20

Define Oedema?

Answer 20

Build up of fluid in the interstitial space

Question 21

What is the effect of plumonary oedema on the lungs?

Answer 21

diffusion distance increases - gas exchange compromised. Compliance in the lungs is also affected

Question 22

What are the causes of Oedema? (briefly)

Answer 22

1. Raised capillary pressure
   - Arteriolar dilatation
   - Raised venous pressure
2. Reduced plasma osmotic pressure
   - Normal = 65-80 g/l
   - Oedema = 30 g/l
   - Causes: malnutrition, protein malabsorption, excessive renal excretion of protein, hepatic failure
3. Lymphatic insufficiency
   - Lymph node damage
   - Filariasis – elephantiasis
4. Changes in capillary permeability
   - Inflammation
   - Histamine increases leakage of protein