1. Defending Against Pathogens

2. First Line of Defence Once a pathogen enters body it can make you ill.... First line of Defence: a barrier to stop entrance of pathogens Skin – acts like a seal keeping the internal and external environment separate Mucus – internal areas that can be exposed to outside environment covered in mucus membranes

3. What is Mucus?? Sticky, slimy material produced constantly by the body to act as a surface to trap pathogens and other debris from entering body When sick, mucus membranes trap pathogens and expel them with runny noses and sneezes

4. How does first line fail? Breaks in skin leave tissue underneath exposed Small cracks in tissue can be microscopic and not seen/detected Some skin is thinner than other parts and is easily damaged (ie; inside of nose)

5. Second Line Cells called Macrophages cycle through blood stream and gobble up pathogens White blood cells who detect invaders and eat them Process kills both the macrophage and the pathogen Excess macrophages = pus

7. Third Line When pathogens are too numerous antibodies are required Antibodies are small particles that your body makes Each antibody is designed for a certain antigen (a foreign material in the body)

9. General vs Specific Defence General defence = mechanisms that attack any pathogen (1 st and 2 nd line) Specific defence = mechanism to recognize and attack one type of pathogen (3 rd line)

10. How do they work? Antibodies work by binding to the antigens surface The binding signals immune system to increase production of that antibody New antibodies continue to bind to antigen and render it useless (kind like tackling a running back in football)