system
Given the following post, respond as if you're commenting on Reddit:
human
How is O2 introduced to blood in the alveoli?

Are streams of O2 and blood introduced into the same space and given time to bind?
gpt
It's via diffusion, the deoxygenated blood has a higher affinity for the oxygen and the haemoglobin will bind to the oxygen easily.

Diffusion isn't very efficient, hence needing a very high surface area and very thin capillary walls in the alveoli.

The blood travels along enough of this diffusion-optimised path to ensure (in a healthy person) that almost all the blood becomes saturated.