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Maintenance of the Immune System

Maintenance of the Immune System - THE MAINTENANCE OF...

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THE MAINTENANCE OF BALANCE BY THE IMMUNE SYSTEM 10.1: The Body’s Line of Defence Pathogens are disease causing organisms First Line of Defence: First line of defence by the body against foreign invaders is largely physical The skim and mucous membranes protect against bacterial and viral invaders Human skin provides a protective barrier that cannot be normally penetrated by bacteria or viruses The skin also has chemical defenses in the forms of acidic secretions which kept at a pH range of 3-5 is enough to inhibit the growth of microbes Lysozymes, antimicrobial enzymes are secreted in human tears, saliva, mucous secretions and perspiration breaks and destroys the wall of bacteria, killing them Mucous membranes along your nose, throat secret mucus which then traps dust and foreign particles/debris This trapped particles and dirt is swept back and forth by cilia, tiny hair They sweep the particles toward the entrance where coughing can expel them from the body Corrosive acids in the stomach and protein-digesting enzymes destroy most of the invading microbes carried into the body with food Second Line of Defence: Leukocytes , white blood cells are large, opaque blood cells that may engulf invading microbes or produce antibodies White blood cells have a nucleus, making them easily distinguishable from red blood cells who lack a nucleus One class of leukocytes, granulocytes contain cytoplasmic granules and they are produced in the bone marrow Arganulocytes are white blood cells who do not have a granular cytoplasm and they are also produced in the bone marrow but are modified in the lymph nodes
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The body’s nonspecific defense mechanisms rely mainly on the process of phagocytosis , in which white blood cells engulfs and chemically destroys a microbe There are two main responses: Monocytic Response When a foreign particle penetrates the skin through an injury, special leukocytes called monocytes migrate from the blood and into tissues These monocytes develop into macrophages (“big eaters”) that extend long profusions called pseudopods that attach to the surface of invading microbes The microbe is then engulfed and destroyed by enzymes within the macrophage Neutrophilic Response White blood cells called neutrophils are attracted to chemical signals given off by cells that have been damaged by microbes Other chemicals like histamines and prostaglandins are released by the body The chemical signals cause the capillaries to dilate, resulting increased blood flow and the permeability of capillaries also increase A process called chemotaxis occurs where the neutrophils squeeze out of the capillaries and migrate toward the infected tissue They engulf the microbe and lysosomal enzymes digest both the microbe and the leukocyte The remaining fragments of the protein, dead white blood cells, digested invaders like bacteria are called pus The inflammatory response
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