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Chapter 43-The Immune System.docx

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Department
Biology
Course
BIOL 225
Professor
Ian Ferguson
Semester
Fall

Description
Chapter 42 – The Immune System Protects again potential pathogens, which are microorganisms that can cause disease. The  Immune system develops an innate immunity, which is a rapid response to a broad range  of microbes. Another type is acquired immunity, which is a slower response to a specific  microbe. Innate immunity can be broken down into two divisions: • External defense: skin, mucous membranes, and secretions. • Internal   defenses:   Phagocytic   cells,   antimicrobial   proteins,   inflammatory  response, and natural killer cells. Acquired immunity: • Humoral response: antibodies • Cell­mediated response Innate immunity External defense • Physical barrier o Skin, exoskeleton, lining of trachea, etc. • Chemical barrier o Lysozyme in tears, mucus, saliva, etc.  o HCl in gastric juice Internal defenses • Non self cells must be identified using chemical cues • Immune cells respond to molecules on fungi, bacteria, etc. that are not found in  the self. • Phagocytic cells o Hemocytes in hemolymph of insects • Antimicrobial proteins o Typically interfere with metabolic processes that are foreign to the self o Circulate through the body o Inactivate or kill bacteria, fungi, etc. Chordates Immune System • Antimicrobial proteins o Interferon  Trigger anti­virus defenses o Complement system  Once triggered, a cascade of reactions that creates holes in the  plasma membrane of invading cells. • Phagocytic cells o TLR (Toll­like receptors)­ binds to molecules that are characteristic to  certain types of cells o Leukocytes  Neutrophils • 60­70% of leukocytes  Monocytes • 3­8% of leukocytes • Not   exactly   phagocytic   but   could   develop   into  macrophages • Some take up residence in various tissues • Some found in spleen and lymph nodes  Eosinophil • 2=4% of leukocytes • Enter parasitic worms and release destructive enzymes  Basophils • Release signals that intensify inflammation • 0.5­1%  Lymphocytes • 20­25% • T­Cells o Acquired immunity • B­Cells o Acquired immunity • Natural killer cells o Destroys diseased self cells o Dendritic cells  Often found in connective tissue  Involves in acquired immunity Inflammatory response: If, by accident, you pierce your skin, bacterium will surely come into your skin. Inside  the tissue, microphages engulf the bacteria and kill it. There are also mast cells. What  Mast cells do is they produce histamine, which causes the sphincter to relax, increasing  blood flow into the capillaries. This is done to increase permeability of the capillaries so  that bacterium cannot penetrate. The histamine attracts the neutrophils and monocytes,  which starts the attack towards the bacteria. Acquired Immunity of Vertebrates: Unique among animals and vertebrates Spleen: • Packed with lymphocytes and macrophages • Stores lymphocytes, erythrocytes, and thrombocytes • Remove worn out erythrocytes o Globin   and   iron   from   haemoglobin   are   rec
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