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Chapter 13 - Chapter 13 Microbes and Human Body 0 Normal...

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Chapter 13 Microbes and Human Body 0 Normal Microbiota - microorganisms colonizing the human body without harming it 1 Transient microbes - rapidly lost 2 Pathogenic microbes - invade and damage the cells and tissue Requiring Resident Biota 3 The uterus is germ-free 4 First exposure to microbes occur during the passage through the birth canal 5 Feeding 6 Contact with the environment and family members The Progress of Infection 7 Infection starts with an invasion of a pathogen 8 How successful this invasion will be depends on: 0 Pathogenicity - the ability of a microbe to causes disease in another organism 1 Virulence - the degree of pathogenicity; relative ability of a microbe to causes disease 0 Virulence factors (enzymes, toxins, capsule, etc.) 1 Establishing the Infection 2 •The microbes enter the body through “Portal of Entry” 0 –Mucous membrane (lines the body cavities that are open to the environment) 0 Respiratory tract 0 Is the most common portal of entry? 1 Inhalation (common cold, influenza, pneumonia, tuberculosis) 1 Gastrointestinal tract 0 Food, water, & contaminated hands 1 Hepatitis a, typhoid fever, amoebic dysentery) 2 Genitourinary tract 0 Through sexual contact (STDs) 1 –Skin (openings or cuts) 0 -Tough barrier 1 -Broken skin enables penetration of microbes 2 -Digestive enzyme or microbes 3 -Insect bites 4 -Hypodermic needles 5 -Common infectious agents 0 Staphylococcus aureus (boils) 1 Streptococcus pyogenes (impetigo)
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2 Clostridium (gangrene, tetanus) Preferred Portal of Entry 6 Some pathogens are only effective when inhaled and not swallowed, etc. 3 4 •Attaching to the host 0 -Microorganisms attach themselves to the host cell 0 Fimbriae (bacteria) 1 Capsules (bacteria) 2 Spikes (viruses) 1 -Adherence 0 Attachment is based on binding of specific molecules on both host and pathogen 1 Surface molecules of the pathogens (ligands) bind to the specific molecules of host tissue cells (receptors) 2 Ligands are located on glycocalyx or on fimbriae 5 6 •Surviving host defenses 0
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