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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.
The alveoli is just one cell layer thick so that diffusion of gasses between the capillaries and the alveoli is easy. Simple squamous epithelium are found in the capillary wal â¦ ls and the alveolar walls.They are thin so diffusion is easy.he alveoli is just one cell layer thick so that diffusion of gasses between the capillaries and the alveoli is easy. Simple squamous epithelium are found in the capillary wal â¦ ls and the alveolar walls.