Innate immunity - Pathogen - Host interactions Access...

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Pathogen - Host interactions • Access • Attachment • Evasion of defense mechanisms
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An Overview of the Body’s Defenses Resistance to most plant and animal pathogens Resistance due to physiological processes of humans that are incompatible with those of the pathogen (species resistance) – Correct chemical receptors not present on human cells – Temperature and pH may be incompatible with those necessary for the pathogen’s survival Number of pathogens for which humans don’t have innate resistance can cause disease
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An Overview of the Body’s Defenses Animation: Host Defenses: Overview
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The Body’s First Line of Defense • Made up of structures, chemicals, and processes that work to prevent pathogens entering the body • Includes the skin and mucous membranes of the respiratory, digestive, urinary, and reproductive systems
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The Body’s First Line of Defense The Role of Skin in Innate Immunity – Skin composed of two major layers • Epidermis – Multiple layers of tightly packed cells » Few pathogens can penetrate these layers » Shedding of dead skin cells removes attached microorganisms – Epidermal dendritic cells » Phagocytize pathogens • Dermis – Contains protein fibers called collagen » Give skin strength and pliability to resist abrasions that could introduce microorganisms
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The Body’s First Line of Defense [INSERT FIGURE: 15.1]
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The Body’s First Line of Defense The Role of Skin in Innate Immunity – Skin has chemicals that defend against pathogens • Perspiration secreted by sweat glands – Salt – inhibits growth of pathogens by drawing water from their cells – Antimicrobial peptides – sweat glands secret dermicidins – Lysozyme – destroys cell wall of bacteria • Sebum secreted by sebaceous (oil) glands – Helps keep skin pliable and less likely to break or tear – Lowers the pH of the skin to a level inhibitory to many bacteria
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The Body’s First Line of Defense The Role of Mucous Membranes and the Lacrimal Apparatus in Innate Immunity – Mucous membranes line all body cavities open to the outside environment – Two distinct layers • Epithelium – Thin, outer covering of the mucous membranes – Unlike surface epidermal cells, epithelial cells are living – Tightly packed to prevent entry of pathogens – Continual shedding of cells carries attached microorganisms away • Deeper connective layer that supports the epithelium
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The Body’s First Line of Defense [INSERT FIGURE: 15.2]
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The Body’s First Line of Defense [INSERT TABLE: 15.1]
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The Body’s First Line of Defense The Role of Mucous Membranes
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Innate immunity - Pathogen - Host interactions Access...

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