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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 outer layer of epithelium is called the parietal layer. Blood is filtered out from the capillaries through the visceral layer of epithelium into the capsular (Bowman's) space, and can move out from here into the proximal convoluted tubule.This section shows a renal corpuscle.he outer layer of epithelium is called the parietal layer. Blood is filtered out from the capillaries through the visceral layer of epithelium into the capsular (Bowman's) space, and can move out from here into the proximal convoluted tubule.