What role does oxygen and carbon dioxide play in the circulatory system?

Oxygen and carbon dioxide is exchanged by the millions of alveoli in the lungs and the capillaries that envelop them. we inhale oxygen (which is then exchanged with carbon dioxide in the lungs) and then we exhale the carbon dioxide. although, the air that we breathe usually consists more nitrogen than oxygen.

Ithink a saturated phospholipid