Difusion

Question 1

What determines the amount of O2 that gets dissolved in plasma?
What determines alveolar PO2?
How much O2 will dissolve in plasma at sea level?

Answer 1

Alveolar PO2 (Henry’s Law).
Atmospheric PO2 and alveolar ventilation.
3 (mL O2/L Blood)

Question 2

Explain how pressure gradients drive diffusion of gasses into and out of blood in the lungs

Answer 2

The PO2 and PCO2 in the alveoli are 100 mmHg and 40 mmHg, respectively. When blood enters the lung in the capillaries, the PO2 is 40 mmHg and the PCO2 is 46 mmHg. A Pressure gradient exists for both O2 and CO2. Each gas diffuses across its gradient to create equilibrium.

Question 3

Explain how pressure gradients drive diffusion of gasses into and out of blood in tissue.

Answer 3

As blood enters tissue from the arteries and arterioles, the PO2 is 100 mmHg and PCO2 is 40mmHg. The PO2 and PCO2 in the tissues are 40mmHg and 46mmHg respectively. The gasses move across their gradient to saturate the tissue with oxygen and remove CO2. (actual tissue levels vary)

Question 4

What would Cardiac Output need to be if blood only absorbed 3 mL/L Blood in plasma?

Answer 4

83 L/min

Normal CO is ~ 5 L/min