What does oxygen diffuse into?
Oxygen diffuses from any place there is a lot of it to any place
where there is less. In the body, it diffuses from the air in the
alveoli of the lungs, through the lung and capillary walls and into
the blood, where it is taken up by the haemoglobin of the red blood
cells. When the bood reaches the body tissues it diffuses out of
the blood and into the cells.