bio respiratory

[chiddler]

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nevermind.
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Atmospheric PO2 is 150 torr, while arterial PO2 is 100 torr. Which is the best explanation for this difference?
A. Due to the short amount of time blood spends in the lungs, atmospheric gases do not fully equilibrate with arterial gases.
B. The barrier to diffusion formed by the alveolar epithelium plus the capillary endothelium prevents full equilibration of the atmospheric and arterial gases.
C. The PH2O and PCO2 in the alveolus are much higher than the atmosphere, as a result, PO2 is lower.
D. The hydrophobic nature of oxygen prevents large amounts from dissolving in blood.

Answer

Explanation below.

 

[chiddler]

"A and B are plausible explanations but are not the best answers. Water and CO2 take up a greater proportion of gases in the alveolus than in the atmosphere. The gases in the alveolus do not have the same composition as the atmosphere since they are not fully exchanged with each breath."

oh. ohhh.

typing this out made me understand. nevermind.