Topic 11: Cardiovascular System - Capillary Exchange

Question 1

What is capillary exchange between?

Answer 1

blood and ISF

Question 2

What three methods allow solutes to enter and leave capillaries?

Answer 2

• diffusion
• vesicular transport
• Mediated Transport

Question 3

What is the role of diffusion in capillary exchange?

Answer 3

• major route, except for brain

Question 4

Which ions and molecules can diffusion occur for in capillary exchange? (6)

Answer 4

• CO2
• O2
• ions
• aa
• glucose
• hormones etc

Question 5

Between which cells does diffusion occur?

Answer 5

between endothelial cells

Question 6

Which molecules is vesicular transport for?

Answer 6

large proteins (ie antibodies)

Question 7

How does vesicular transport in capillary exchange occur? (3)

Answer 7

• via transcytosis
• endocytosis from blood into endothelial cell
• then exocytosis from endothelial cell into ISF

Question 8

What does mediated transport require? (2)

Answer 8

• membrane carrier protein
• important mainly for brain

Question 9

Through which mechanisms does fluid (water) enter/absorb or leave/filtrate capillaries? (2)

Answer 9

• osmosis
• bulk flow

Question 10

Why does bulk flow allow for absorption/filtration in capillaries?

Answer 10

• due to pressure differences

Question 11

What 4 pressures are involved in bulk flow of capillaries?

Answer 11

1) Blood hydrostatic pressure (BHP) - blood pressure
2) blood osmotic P (BOP) - due to plasma proteins
3) ISF hydrostatic P (IFHP) - 0 mmHg
4) ISF osmotic P (IFOP) - due to ISF proteins

Question 12

Net filtration pressure (NFP) diagram

Answer 12

Question 13

What is net filtration pressure? (2)

Answer 13

• sum of hydrostatic and osmotic pressures acting on the capillary
• across a capillary from arteriolar to venous end

Question 14

Formula for net filtration pressure

Answer 14

Question 15

Example given of NFP important

Answer 15

• negative means absorption

Question 16

What occurs in the body in NFP? (3)

Answer 16

• 90% of filtered fluid reabsorbed to blood
  -10% enters lymph
• therefore ISF volume remains relatively constant

Question 17

One clinical application of NFP is edema. What is edema? (20

Answer 17

• accumulation of fluid in the tissue (ISF)
• causes swelling

Question 18

What is edema due to? (4)

Answer 18

1) high bp (high BHP)
2) leakage of plasma proteins into ISF, causing inflammation (increased IFOP)
3) decreased plasma proteins (malnutrition, burns) (decreased BOP)
4) obstruction of lymph vessels (elephantiasis, surgery)