Viral Protozoan And Helminthic Diseases Of The

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Viral, Protozoan, And Helminthic Diseases Of The Cardiovascular And Lymphatic Systems Essay, Research Paper Viral, Protozoan, and Helminthic Diseases of the Cardiovascular and Lymphatic Systems Koch s postulates are guidelines for determining that a specific microorganism causes a specific disease. Koch s postulates are as follows: 1. The same pathogen must be present in every case of the disease. 2. The pathogen must be isolated from the diseased host and grown in pure culture. 3. The pathogen from the pure culture media must cause the disease when it is inoculated into a healthy, susceptible laboratory animal. 4. The pathogen must be isolated from the inoculated animal and must be compared to the original pathogen. Microorganisms can enter the body in a variety of ways.

They can penetrate the mucous membranes of the respiratory, gastrointestinal, genitourinary systems and the conjunctiva, the membrane that covers the eyes. Microbes can easily be inhaled through the respiratory tract. They can also be ingested in contaminated food. Some microorganisms enter the body through the skin. Some microbes, such as fluke worms, can burrow through the skin into the bloodstream. Bacteria, viruses, and protozoan can go through the skin via a bite, cut, or other wound; this is called parenteral entry. Bacteria have several devices which they use to penetrate the host s defenses. Some have capsules or proteins in the cell wall that prevent them from being phagocytized. Some can even reproduce in a phagocyte. Bacteria can also produced enzymes such as

leukocidins to destroy neutrophils and macrophages and hemolysins that cause lysis in red blood cells. Bacteria damage host cells and induce illness in two ways: direct damage and the production of toxins. Bacteria damage and destroy the host cells as they multiply. Bacteria also produce toxins, which are substances poisonous to the host. They release exotoxins, which produce disease symptoms. Cytotoxins kill host cells or affect their functions. Neurofunctions interfere with nerve transmissions. Enterotoxins affect cells lining the gastrointestinal tract. The death of the bacterial cell or the presence of antibodies or antibiotics can trigger the release of endotoxins. They can lead to fever and shock. Plasmids are DNA molecules in bacteria that may carry genes for antibiotic

resistance, toxins, capsules, and fimbriae. Lysogeny is bacteria infected with viruses that can change the virulence by altering the toxins or the capsule. Viruses evade the immune system by growing inside the host cells, where the body s defenses cannot reach. They can easily invade host cells because they have attachment sites for receptors on the host cell. Viruses can causes cytocidal and noncytocidal effects (cell death and cell damage, respectively). Other effects include the stopping of mitosis, lysis, cell fusion, antigenic changes, and transformation of cells. Fungus cause problems in the host with capsules, toxins, and allergic responses. Protozoan and helminths cause disease by damage the host tissue or by the wastes they produce. Some protozoa can change their surface

antigens while growing so that the host s antibodies do not kill the protozoa. Algae can be harmful to the host as some can produce neurotoxins. Nonspecific defense mechanisms are the body s defenses against any pathogen. The first defense of the body is the skin. Intact skin is impenetrable for most microorganisms. The protein keratin in the skin makes it resistant to microbial invasion. Mucous membranes line the respiratory, gastrointestinal, and genitourinary tracts and are also a barrier for invading pathogens; these can readily trap microbes attempting to enter these systems. Phagocytosis is the ingestion of microorganisms by a cell. It is performed by phagocytes and white blood cells. White blood cells, or leukocytes, are divided into three groups: granulocytes,