Outside air needs to be heated and moistened to match the body's temperature and humidity. As air passes down the tracheobronchial tree, it is warmed and water is added. Contaminants must also be removed. Nose hairs and tiny microscopic hairs called cilia, along with sticky mucus produced by the lining membrane help cleanse the air of impurities. Cilia beat in a synchronized fashion brushing any collected dirt and mucus up toward the mouth. The accumulated material is then coughed out or swallowed. By the time the air reaches the alveoli, it is virtually sterile. Amazingly, all of the above is occurring naturally while you are reading this information!
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