Inside the air sacs, oxygen moves across paper-thin walls to tiny blood vessels called capillaries and into your blood. A protein called haemoglobin in the red blood cells then carries the oxygen around your body.

How oxygen diffuses from the air in the alveolus into the blood?

In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries (tiny blood vessels) lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells.

Does oxygen diffuse out of blood?

Oxygen diffuses through the cell membrane and is transported in blood plasma by free diffusion and by convection.