The Immune System

The Immune System - The Immune System P A R T A 1 Immunity:...

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Unformatted text preview: The Immune System P A R T A 1 Immunity: Two Intrinsic Defense Systems n Innate (nonspecific) system responds quickly and consists of: First line of defense skin and mucosa prevent entry of microorganisms Second line of defense antimicrobial proteins, phagocytes, and other cells n Inhibit spread of invaders throughout the body n Inflammation is its most important mechanism 2 Immunity: Two Intrinsic Defense Systems n Adaptive (specific) defense system Third line of defense mounts attack against particular foreign substances n Takes longer to react than the innate system n Works in conjunction with the innate system 3 Innate and Adaptive Defenses 4 Innate Defense - First Line n Surface Barriers: skin and mucosa n Skin, mucous membranes, and their secretions make up the first line of defense n Keratin in the skin: Presents a physical barrier to most microorganisms Is resistant to weak acids and bases, bacterial enzymes, and toxins n Mucosa provide similar mechanical barriers 5 Innate Defense n Epithelial membranes produce protective chemicals that destroy microorganisms Skin acidity (pH of 3 to 5) inhibits bacterial growth Sebum contains chemicals toxic to bacteria Stomach mucosa secrete concentrated HCl and protein-digesting enzymes Saliva and lacrimal fluid contain lysozyme 6 Innate Defense Mucus traps microorganisms that enter the digestive and respiratory systems n Respiratory Tract Mucosae: Mucus-coated hairs in the nose trap inhaled particles Mucosa of the upper respiratory tract is ciliated Cilia sweep dust- and bacteria-laden mucus away from lower respiratory passages 7 Innate Defense - Second Line n Internal Defenses: Cells and Chemicals n The body uses nonspecific cellular and chemical devices to protect itself Phagocytes and natural killer (NK) cells Antimicrobial proteins and tissue fluid, fever Inflammatory response enlists macrophages, mast cells, WBCs, and chemicals n Harmful substances are identified by surface carbohydrates unique to infectious organisms 8 Innate Defense Second Line n Phagocytes n Macrophages are the chief phagocytic cells n Free macrophages wander throughout a region in search of cellular debris n Kupffer cells (liver) and microglia (brain) are fixed macrophages n They derive from monocytes 9 Innate Defense Second Line n Neutrophils become phagocytic when encountering infectious material n Eosinophils are weakly phagocytic. They are important against parasitic worms They degranulate their enzymes when encountering the parasite n Mast cells release histamine and heparin 10 Figure 21.2b (b) Lysosome Microbe adheres to phagocyte. Phagocyte forms pseudopods that eventually engulf the particle....
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The Immune System - The Immune System P A R T A 1 Immunity:...

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