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In the alveoli, oxygen from the air is absorbed into the blood. Carbon dioxide, a waste product of metabolism, travels from the blood to the alveoli, where it can be exhaled. Between the alveoli is a thin layer of cells called the interstitium, which contains blood vessels and cells that help support the alveoli.
attached to the outer walls of alveoli are many tiny blood vessels called capillaries essentially the capillaries are like a netting covering the alveolar sacs the place where the capillary tissue meets the alveolar tissue creates an extremely thin layer that molecules can pass throughir is inhaled and travels through into the lungs bronchi bronchioles and finally into the alveoli here o2 passes through the respiratory membrane and into a capillary it is now in the bloodstream where it binds to a red blood cell and travels through the blood to an area where it is needed