1. Science 8 Life Science Lesson L5 ~ The Immune System

2. Four Ways to Transmit Infectious Diseases
Transmission Method
Example
Direct Contact
shaking hands, sharing drinking containers, sharing bodily fluids
Indirect Contact
being near someone who coughs or sneezes (some pathogens can travel up to 5 metres)

3. Four Ways to Transmit Infectious Diseases
Transmission Method
Example
Water & Food
eating foods that are infected (ex: salmonella) or drinking infected water (ex: E coli)
Animal Bites
being bitten by an animal carrying the rabies virus

4. The Immune System
Bacteria and viruses are everywhere! The body has many different ways to protect itself
First Line of Defense ~ barriers that prevent pathogens from getting into the body
Second Line of Defense ~ if a pathogen gets past the first line of defense (often due to tissue damage), your body can mount a secondary immune response to attack and destroy the invader

5. First Line of Defense
Skin ~ physical barrier that stops most pathogens from entering the body
Sweat & Oil on Skin ~ slightly acidic so they prevent some pathogens from growing on the surface of the body
Tears & Saliva ~ contain an antibacterial enzyme (lysozyme) that breaks down bacterial cell walls

6. First Line of Defense
Ear Wax ~ traps foreign materials entering the ear canal (dirt, plant, small insects)
Gastric Juice in Stomach ~ acidic so it can destroy pathogens that enter the stomach
Mucus & Cilia (Hair) in Nose ~ prevent pathogens from entering your respiratory system

7. Second Line of Defense ~ Innate Immune Response
quick and general; same response for anything the body recognizes as an invader (like the common cold virus)
we are born with this defense

8. Second Line of Defense ~ Innate Immune Response
first action is a flow of fluid, cells, and dissolved substances from the blood to the site of the infection; causes a fever and inflammation (swelling and redness)
second action is phagocytes swallowing the invader cells; phagocytes are a type of white blood cell

9. Second Line of Defense ~ Acquired Immune Response
slower but highly specific attack on a particular pathogen (disease-causing organism or substance) or an antigen (non-living particle or substance)
we build up this type of response over time

10. Second Line of Defense ~ Acquired Immune Response
two different processes, both involving types of white blood cells (B cells and T cells)
acquired immune responses help give you active immunity: memory B cells store antibodies and can be reactivated if the antigen or pathogen reappears (that’s why we only get chicken pox once)

11. Second Line of Defense ~ Acquired Immune Response
B cells ~ produce antibodies that attach to and destroy both antigens and pathogens carrying antigens

12. Second Line of Defense ~ Acquired Immune Response
T cells ~
helper T cells recognize the presence of an antigen or pathogen and activates B cells to destroy the antigen or pathogen
killer T cells recognize the presence of an antigen or pathogen and works independently to destroy the antigen or pathogen