Alveoli Gas Gradient Doubt

[rpdnathan]

Can someone help me make sense of this?

The question stem states that the physiological dead space is not involved in gas exchange. This
means that the composition of air in the dead space is virtually identical to that of atomospheric
air. In the alveoli, where gas exchange occurs, oxygen is taken up by the blood and carbon dioxide
is released. Thus, the air in the alveoli will have a lower pO2 and a higher pCO2 than dead space
air. Conversely, dead space air will have a higher pO2 and a lower pCO2 than alveolar air.

I thought alveoli would have higher pO2 because O2 needs to diffuse from alveoli into the bloodstream in order to oxygenate the blood as CO2 is displaced. Please help me clear this doubt. Thank you.

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[MT Headed]

(pO2 atmosphere) = (pO2 dead space) > (pO2 alveoli) > (pO2 blood)

Now, depending on the exact instant you take a snapshot of things in the lungs, the equals sign on the left might become a greater-than sign, and the greater-than sign on the right might become an equals sign, but you get the general idea.

Nobody "pumps" oxygen, so it travels down its concentration gradient.