Immunology - 18 18 to pathogens Animal Defense Systems...

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18 Natural Defenses against Disease 18 Animal Defense Systems Humans are nutritious and taste good ! ... to pathogens ! ° Possible pathogens: ° viruses ° bacteria ° single-cell eukaryotic parasites (yeast) ° parasitic worms ° maggots ° lions? (usually not considered “pathogens”) ° The immune system is a set of mechanisms that protect an organism from infection by identifying and killing pathogens. Decaying mole: 40 hours compressed to 30 sec http://www.youtube.com/watch?v=cb7wBQIR2_0 What happens in the absence of an immune system? 18 Animal Defense Systems Decaying mole: 40 hours compressed to 30 sec http://www.youtube.com/watch?v=cb7wBQIR2_0
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18 Animal Defense Systems ! The immune system must be absolutely specific and not attack normal cells and tissues. ! Pathogens are constantly evolving new ways to avoid detection by the immune system: the immune system must be adaptive . ! The immune system must recognize and defeat pathogens: " viruses " bacteria " single-cell eukaryotic parasites fungi (yeast) " parasitic worms " maggots 18 Animal Defense Systems There are two general types of defense mechanisms: ! Nonspecific defenses, or innate defenses, are inherited mechanisms that protect the body from many different pathogens: The Innate Immune System ! Specific defenses are adaptive mechanisms that protect against specific targets: The Adaptive Immune System Innate immune system Adaptive immune system Response is non-specific Pathogen and antigen specific response Exposure leads to immediate maximal response Lag time between exposure and maximal response Cell-mediated and humoral components Cell-mediated and humoral components No immunological memory Exposure leads to immunological memory Found in nearly all forms of life Found only in jawed vertebrates 18 Who are the players?
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18 The players Components of the defense system are distributed throughout the body. Lymphoid tissues (thymus, bone marrow, spleen, lymph nodes) are essential parts of the defense system. ! Blood (closed circulatory system): suspends red and white blood cells and platelets. " Red blood cells are found in the closed circulatory system. " White blood cells and platelets are found in the closed circulatory system and in the lymphatic system. 18 The players: lymphatic system Lymph consists of fluids that accumulate outside of the closed circulatory system in the lymphatic system . The lymphatic system is a branching system of tiny capillaries connecting larger vessels. These lymph ducts eventually lead to a large lymph duct that connects to a major vein near the heart. At sites along lymph vessels are small, roundish lymph nodes . Lymph nodes contain a variety of white blood cells. The lymphatic system resembles a drainage system 18
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18 18 The players: the human lymphatic system 18 The players: Blood cells White blood cells ( leukocytes ) are important in defense.
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