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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.
Conclusion Questions 3.3.1 1. The walls of the alveoli in the lungs are incredibly thin. Explain how this structure is related to function in the body. The walls of the alveoli are extremely thin so that they can serve their purpose of allowing diffusion of oxygen and carbon dioxide to happen. This is where gas exchange occurs.