Oxygen is inhaled and absorbed into the bloodstream through the thin wall of each alveolus, and carbon dioxide is passed the other way (from the blood to the lungs) to be exhaled.
(Oxygen; is inhaled; ) (Oxygen; absorbed; into the bloodstream) (carbon dioxide; is passed; ) (carbon dioxide; to be exhaled; )
Oxygen Oxygen carbon dioxide carbon dioxide
is inhaled absorbed is passed to be exhaled
into the bloodstream