[Krista B]

I am looking for help on my homework. The question is why does oxygen move form the alveoli into the pulmonary capillary blood? Thank you for all the help you can give me.

[Nanner]

In simple terms, it's called diffusion. Gases tend to move from areas of higher concentration to areas of lower concentration in an attempt to equalize themselves much like areas of high pressure to areas of low pressure areas...since the O2 concentration is higher in the Alveoli ( 21 % from the air breathed in verses ~16 % in the"deoxygenated"blood returning ) than the incoming blood, it moves in that direction. The same but opposite is true for CO2 elimination- it's higher in the blood than the alveoli so it is eliminated into the air breathed in.Have a blessed day- hope that answered your question :-)