Blood Supply and Gas Exchange

Question 1

What is the function of the Bronchial Arteries?

Answer 1

The supply nutrients to the lungs.

Question 2

Describe two features of the Pulmonary Circulation.

Answer 2

High Flow- contains the same volume of blood as passes around the entire body.
Low pressure- 1/5 of the pressure of the systemic arteries.

Question 3

By which process does air pass across the alveolar membrane?

Answer 3

Simple diffusion- down the concentration gradient

Question 4

What two factors determine the rate of diffusion?

Answer 4

• Solubility of gas

- Partial Pressure of gas

Question 5

How does the solubility of Carbon Dioxide differ to the of O2?

Answer 5

Carbon dioxide is much more soluble in water/blood than O2.

Question 6

How does the difference in solubility impact on the size of the concentration gradient?

Answer 6

Carbon dioxide has a much smaller concentration gradient than oxygen.

• 40-46 (pulmonary vein to pulmonary artery)
• 100-40 (pulmonary vein to pulmonary artery)

Question 7

What other factors affect the rate?

Answer 7

• Surface area (emphysema reduces)

- Thickness of the membrane- thick membrane (fibrosis) = barrier to diffusion

Question 8

How does pulmonary oedema effect diffusion?

Answer 8

Fluid increases the distance over which gases diffuse.

Question 9

How does asthma effect diffusion?

Answer 9

No effect on diffusion but ventilation is reduced so partial pressure of co2 and o2 are decreased.

Question 10

What is the relationship between air in the alveoli and the local blood flow.

Answer 10

Should overall be in equilibrium.

• Base= ventilation > perfusion (fluid pools)
• Apex= perfusion > ventilation (air rises)

Question 11

How does the body respond to a decrease in ventilation?

Answer 11

• PaO2 decreases
• PaCO2 increases
• Cells detect hypoxia
• Pulmonary Vasoconstriction= less blood flows to the damaged alveoli.
• Mild bronchodilation increases airflow.

Question 12

How does the body respond to a decrease in blood flow?

Answer 12

• Blood clot or embolism restricts the blood flow.
• creates ALVEOLAR DEAD SPACE
• pulmonary vasodilation
• bronchoconstriction.

Question 13

What is Alveolar dead space?

Answer 13

Air that is in the alveoli but there is no perfusion so no gas exchange.

Question 14

What is anatomical dead space?

Answer 14

Air in the conducting airways that does not take part in gas exchange.