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E2.Defense - Body Defenses Pathogens Pathogen an agent...

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Body Defenses Heyer 1 Body Defenses Pathogens & Immunity Pathogens Pathogen: an agent causing a disease Microbe: microscopic organism (most are not pathogens) – Bacteria – Protists (eukaryotic, single-celled) – Multicellular (fungi, parasites) Infectious particles (non-living) – Viruses: nucleic acids wrapped in protein capsid – Prions: rogue proteins Pathogens First line of Defense: Barriers Stratified squamous epithelia – Skin; mucous membranes Flushing action – Urine, tears, saliva, sweat, oil glands Mucus traps – Respiratory, digestive, and vaginal tracts Lysozyme (enzyme digests bacterial walls) – Tears, sweat, saliva Acidic pH – Stomach, vaginal secretions High body temperature Competition from microflora (resident microbes) Second line of Defense: Non-specific Responses Macrophages and Fixed Phagocytes – Phagocytosis of any “non-self” cell • Inflammation Inflammatory Response Hallmark symptoms of inflammation: redness, heat, swelling and pain
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Body Defenses Heyer 2 Third line of Defense: Specific Responses (Immunity) The Lymphatic System B-lymphocytes & antibody-mediated defense Esp. vs. bacteria, chemical toxins, & free viruses T-lymphocytes & cell-mediated defense Esp. vs. eukaryotic pathogens: parasites, viral-infected cells, cancerous cells, & transplanted tissues The Lymphatic System Lymphatic circulation Lymphoid tissues The Lymphatic System Lymphatic circulation Lymphatic vessel with valve The Lymphatic System Lymphoid tissues The Lymphatic System
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