Download Chapter 21, Lesson 2 – Defense Against Disease

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