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.
when we inhale the air the aur goes to the lungs through wind pipe there is alveoli present in lungs which helps in separation of co2 and o2 and then it sent o2 to the blood through walls .
