113lecture2306

113lecture2306 - BIOLOGY 113 - MICROBIOLOGY Lecture 23:...

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BIOLOGY 113 - MICROBIOLOGY Lecture 23: Nonspecific Host Defenses - Barriers, formed blood elements, inflammation, complement Host resistance refers to an animal's ability to defent against infection by pathogenic microorganisms - Nonspecific resistance refers to defenses that protect us from any kind of pathogen - Specific resistance, sometimes called specific immunity, refers to specialized forms of resistance that are pathogen-specific - Contributing to nonspecific resistance are physical and chemical barriers, phagocytosis, inflammation, fever, and complement activation Physical and chemical barriers prevent access of pathogens to tissues - The outer layer of our skin's epidermis is dead and and contains a high concentration of keratin, which prevents microorganisms from penetrating it to the underlying dermis - The mucous membranes that cover many exposed epithelial cell layers provide some protection, but are often penetrated by microorganisms - The lacrimal apparatus (Tortora et al., Figure 16.3) provides a continuous washing action for protection of the eyes; similarily, saliva may prevent colonization of mouth and upper respiratory tract surfaces, urine flow may prevent colonization of the bladder, and vaginal secretions may move microorganisms out of the vagina - Respiratory and gastrointestinal tracts are protected by mucous membranes = The mucus may help to trap microorganisms = The epithelial cells of the lower respiratory tract are ciliated; the action of this ciliary escalator moves mucus, along with trapped particles and microorganisms, up into the throat - A variety of secretions serve as chemical defenses
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113lecture2306 - BIOLOGY 113 - MICROBIOLOGY Lecture 23:...

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