gas exchange

Question 1

1

Answer 1

Exchange across systemic capillaries also occurs down partial pressure gradients

Question 2

2

Answer 2

By equilibration in the alveoli, the oxygen in the systemic capillaries has a high partial pressure (e.g., 100) compared to tissue cells (e.g., 40). These cells are using oxygen.

Question 3

3

Answer 3

The partial pressure for carbon dioxide in the systemic capillaries is low (e.g., 40) compared to the tissue cells (e.g., 46), which are making this gas through their metabolism.

Question 4

4

Answer 4

By partial pressure gradients, oxygen diffuses from the systemic capillaries into the tissue cells (100 to 40, higher to lower). Carbon dioxide diffuses in the opposite direction.

Question 5

5

Answer 5

Having equilibrated with the tissue cells, the blood leaving the systemic capillaries is low in oxygen and high in carbon dioxide.

Question 6

6

Answer 6

This blood returns to the right side of the heart and on to the lungs. At the pulmonary capillaries, the blood acquires oxygen and releases some of its carbon dioxide.

Question 7

Additional factors that affect the rate of gas transfer across alveolar membrane:

Answer 7

• As surface area increases, the rate increases
• Increase in thickness of barrier separating air and blood decreases rate of gas transfer
• Rate of gas exchange is directly proportional to the diffusion coefficient for a gas
• Partial pressure gradients of Oxygen and Carbon Dioxide
• Diffusion Constant

Question 8

Why are approximately equal amounts of CO2 and O2 transferred across the alveolar membrane?

Answer 8

The diffusion constant for CO2 is 20x that of O2, offsetting the smaller partial pressure gradient for CO2