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Defenses Against Disease Chapter 21, Lesson 2 Pruitt, Allegrante, Prothrow-Stith, Health, Pearson, 2014 Write: for each of your responses, explain how your behavior could affect your chances of getting or spreading an infectious disease. QUICK QUIZ: Complete each of these statements with always, sometimes, or never. 1. I ____ wash my hands before meals. 2. When preparing fruits and vegetables, I ___ wash them thoroughly. 3. I am ___ careful to use only my own eating utensils, drinking cups, towels, toothbrush, and grooming items. 4. I ___ cover my mouth when I cough or sneeze. 5. If I spend time in wooden areas, I ___ wear insect repellent. Physical & Chemical Defenses • Skin – both physical and chemical • Surface cells hard and have no gaps • Sweat – chemical barrier – contains acids that kill many bacteria • Old skin cells shed constantly so pathogens on those cells shed also • Microorganisms cannot get through skin unless there is a cut, scrape, burn, or other injury Mucous Membranes • Openings to mouth, eyes, nose – covered • Secrete mucus, trapping many pathogens and wash them away; also contain chemical that attack pathogens Cilia • Working with mucus, pathogens are trapped and removed • Cough, sneeze, or blow nose – pathogens removed along with mucus Saliva and Tears • Trap pathogens and wash away • Contain chemicals that attack pathogens Digestive System • Chemicals – acids in stomach – kill many pathogens • Normal work of digestive system also expels pathogens • Bacteria normally live in digestive tract that harm and kill invading bacteria Inflammation • Body’s general response to all kinds of injuries • Fights infection and promotes healing process Phagocytes • Blood, other fluids, and white blood cells • Leak out, engulf, and destroy pathogens • Give off substances that cause healing • Fluids, phagocytes, and dead cells accumulate at injury site to form pus • Eventually inflammation process heals damage The Immune System • Fight disease by producing separate set of weapons for each kind of pathogen encountered Immune Response • Pathogen first entry causes disease • Body builds defense • Once defense built, body kills pathogen and healing begins • Lymphocytes – white blood cells – carry out immune system’s functions • If pathogen tries to enter again, body remembers and launches immediate attack • Immunity – body’s defense system against returning pathogens T Cells • Killer T cells – destroy any body cell that has been infected by pathogen • Helper T cells – produce chemicals to stimulate other T cells and B cells to fight off infection • Suppressor T cells – produce chemicals that “turn off” immune system cells when pathogen is under control • Help immune system “remember” pathogens • This “memory system” is what causes one to develop an immunity when previous infection tries to invade body again B cells • Produce antibodies – attach to surface of pathogen or toxin • Keeps body free from harm • Each type of B cell attacks specific pathogen or toxin • Infection overcome, antibody production stops, but remembers how to build them again Lymphatic System • Network of vessels collecting fluid from tissues and return it to bloodstream • Fluid flowing – lymph • Lymph nodes – filtering station – phagocytes and lymphocytes found here and attack pathogen as it tries to move through Passive Immunity • Immunity acquired by receiving antibodies from source other than the immune system • Temporary • Occurs naturally in babies – from mom before birth and continue from mom through breast milk • Artificially acquired – injection from doctor Active Immunity • Created by your system • Acquired by either having a disease or from receiving a vaccine • Immunizations or vaccinations as a child • Produce antibodies against disease for which you were immunized • May need booster • May need additional immunizations due to work, travel, exposure to unusual pathogen • May need because of risk factors – age, poor health – influenza immunization for elderly