March 2, 2010 Notes

March 2, 2010 Notes - Chapter 43 Defense against Disease:...

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Unformatted text preview: Chapter 43 Defense against Disease: The Immune System The first time you are exposed to a flu strain, it takes you a very long time to recover. If you become infected with the flu strain a second time, your immune system can defend against this strain much better. Three lines of defense against microbial attack o See figure 43.2 o Two kinds Defenses Innate defenses Nonspecific external barriers Nonspecific internal defenses Acquired immunity defenses o Three lines of defense(specific): External barriers Skin o Physical barrier to microbial entry. o Physical barrier inhospitable environment for growth; dry, dead cells at surface. Sweat/sebaceous glands secreting acids and natural antibiotics like lactic acid. Skin is not a very good place for dead microbes to live We give off lots of enzymes from our skin, which act as natural antibiotics Mucous membranes of respiratory and digestive tracts well-defined. Secretions have antibacterial enzymes. o By drinking a lot of water during cold and flu season, it makes the mucous membranes moister and less susceptible to infection. Stomach; if microbes are swallowed, acids and protein-digesting enzymes destroy them. This is an external barrier because they havent gained access to your tissues. Nonspecific internal defense(if any of the external barriers fail) Phagocytic cells: white blood cells in extracellular fluid, amoeboid shape, destroy microbes by phagocytosis. o These are made in bone marrow, and they mature in the bone marrow. o See figure 43.1 Natural killer cells: White blood cells that destroy body cells infected by viruses and cancerous cells by punching holes in them. o If one of your cells is infected, your body can recognize this and the natural killer cells will kill it by pore-forming proteins inserting into the plasma membrane of the infected cell, self-assembling into large pores. Inflammatory response: caused by large-scale microbial invasion through wound, such as mosquitoes or gnat bites. o Allergies are an example of the inflammatory gone bad against pollen. o Your body responds by the damaged cells releasing histamine. Histamine increases blood flow and washes out the wound. Can also change the permeability of the walls of the capillaries to allow white blood cells to flow in. At the area with increased blood flow, it becomes inflamed (red, swollen, warm). When those cells happen because of injury, such as breaking of the skin, other chemicals enter into the cells, and macrophages (white blood cells that engulf bacteria, dirt, and tissue debris) clean up the mess. This is where puss comes from. The histamine causes white blood cells to leave the area....
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March 2, 2010 Notes - Chapter 43 Defense against Disease:...

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