How the Immune System Works

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Most of the time nonspecific defenses keep pathogens from getting into the body. Sometimes one can break through and cause a disease. This is where the immune system comes into use. The immune system is the body's third line of defense. It is a network of several tissues and white blood cells. The tissues of the immune system are bone marrow, thymus, lymph nodes, spleen, tonsils, and adenoids. The white blood cells of the immune system are called lymphocytes (Postlethwait Hopson, Modern Biology). The job of the immune system is to keep “foreign” invaders out of the body, or if one gets in, to seek it out and kill it. These foreign invaders are called pathogens, which are tiny organisms that can cause an infection in the body. Pathogens can be bacteria, parasites, and fungi (http://www.niaid.nih.gov/topics/immuneSystem/pages/whatisimmunesystem.aspx). Each part of the immune system plays a certain role in keeping pathogens out of the body. Bone marrow is the soft material found inside bones. It is used to make the lymphocytes needed in the body every day. Located above the heart, the thymus is a gland that helps produce a special kind of lymphocyte. Located throughout the body along the vessels of the lymphatic system are the lymph nodes. Lymph nodes contain lymphocytes. Lymph nodes collect pathogens from the lymph and expose them to lymphocytes. The largest lymphatic organ in the body is the spleen. The spleen stores healthy blood cells and breaks down aging red blood cells. It also helps make lymphocytes and other types of red blood cells. Another function of the spleen is it collects pathogens from the blood and attacks the trapped pathogens. The adenoids are masses of lymph tissue found in the nose and throat. The two ... ... middle of paper ... ...would be able to survive without the help of the immune system. Works Cited “Cells Involved In Immune Responses and Antigen Recognition.” Microbiology and Immunology. Web. 18 Dec. 2011. . “Immune Response: MedlinePlus Medical Encyclopedia.” National Library of Medicine - National Institutes of Health. Web. 18 Dec. 2011. . Lechtenberg, Richard. "Multiple Sclerosis Fact Book." F.A. Davis Company, 1988. “Modern Biology, (0030565413), Holt Rinehart & Winston.” Web. 18 Dec. 2011. Neustaedter, Randall. The Immunization Decision. North Atlantic Books, 1990. “What Is the Immune System.” National Institute of Allergy and Infectious Diseases Home Page. Web. 18 Dec. 2011. .

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