usually stops these invaders from getting in.
             The primary way to stop pathogens is by the skin. But, the skin has natural openings where they can get in. The eyes, ears, nose, mouth, and genitals are all natural openings.
             The second line of defense is at these natural openings. The pathogens get stuck in the mucus lining of the nose and mouth or are killed by the saliva and stomach acids; tears from the eyes;
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