Chapter 43 The Immune System. Concept 43.1: Innate immunity provides broad defenses against...
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Transcript of Chapter 43 The Immune System. Concept 43.1: Innate immunity provides broad defenses against...
![Page 1: Chapter 43 The Immune System. Concept 43.1: Innate immunity provides broad defenses against infection A pathogen that breaks through external defenses.](https://reader035.fdocuments.us/reader035/viewer/2022062321/56649f2b5503460f94c45394/html5/thumbnails/1.jpg)
Chapter 43
The Immune System
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Concept 43.1: Innate Concept 43.1: Innate immunity provides broad immunity provides broad defenses against infectiondefenses against infection• A pathogen that breaks through external
defenses encounters innate cellular and chemical mechanisms that impede its attack
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External Defenses
• Skin and mucous membranes are physical barriers to entry of microorganisms and viruses
• Secretions of the skin and mucous membranes provide an environment hostile to microbes
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External Defenses
• Secretions give the skin a pH between 3 and 5, acidic enough to prevent colonization of many microbes
• Skin secretions include proteins such as lysozyme, which digests bacterial cell walls
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External Defenses
• Mucous membrane cells produce mucus, a viscous fluid that traps microbes and other particles
• In the trachea, ciliated epithelial cells sweep mucus and any entrapped microbes upward, preventing microbes from entering the lungs
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Internal Cellular and Chemical Defenses
• Internal cellular defenses depend mainly on phagocytosis
• White blood cells called phagocytes ingest microorganisms and initiate inflammation
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Phagocytic Cells
• Phagocytes attach to prey via surface receptors and engulf them, forming a vacuole that fuses with a lysosome
PseudopodiaMicrobes
MACROPHAGE
Lysosomecontainingenzymes
Vacuole
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• Macrophages, a type of phagocyte, migrate through the body and are found in organs of the lymphatic system
• The lymphatic system defends against pathogens
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Adenoid
Tonsil
Lymphnodes
Peyer’s patches(small intestine)
Spleen
Appendix
Lymphaticvessels Lymph
nodeMasses oflymphocytes andmacrophages
Lymphaticvessel
Bloodcapillary
Tissuecells
Lymphaticcapillary
Interstitialfluid
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The Lymphatic System
• Drains excess fluid– Into veins near the heart
• Temporary reservoir for fluids• Carry hormones throughout the body• Carries fat molecules to the regular
vessels• Part of the immune system
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Diseases of the Lymphatic System
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Antimicrobial Proteins
• Proteins function in innate defense by attacking microbes directly or impeding their reproduction
• About 30 proteins make up the complement system, which causes lysis of invading cells and helps trigger inflammation
• Interferons provide innate defense against viruses and help activate macrophages
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Inflammatory Response
• In local inflammation, histamine and other chemicals released from injured cells promote changes in blood vessels
• These changes allow more fluid, phagocytes, and antimicrobial proteins to enter tissues
Pathogen Pin
Chemical signals
CapillaryPhagocytic cells
Macrophage
Red blood cell
Bloodclottingelements
Blood clot
Phagocytosis
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Natural Killer Cells“better safe than sorry”
• Natural killer (NK) cells attack virus-infected body cells and cancer cells– Recognizes cells that contain “non-self” proteins
• They trigger apoptosis in the cells they attack