cilia
Mucous membranes provide a mechanical barrier at body openings. They also line the respiratory, GI, urinary, and reproductive tracts. Mucous membranes secrete mucus , a slimy substance that traps pathogens. The membranes also have hair-like cilia. The cilia sweep mucus and pathogens toward body openings where they can be removed from the body. When you sneeze or cough, pathogens are removed from the nose and throat see Figure below . Tears wash pathogens from the eyes, and urine flushes pathogens out of the urinary tract. You can watch the sweeping action of cilia at the following link: http://mcdb. colorado. edu/courses/2115/units/Other/mucus%20animation. swf .