1. Starter (from the end of last lesson) 1.What are the similarities between a virus and bacteria? 2. What are the main differences between a virus and bacteria? 3. Draw a flow diagram to explain how viruses replicate. 4. Name three viral diseases. 5. Why are viral diseases much harder to treat than bacterial diseases? 1. How are diseases spread? Title: Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

2. Ways of Spreading Diseases There are four main ways that pathogens are spread from one person to another. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in? Droplet Infection Direct Contact Contaminated Food and Drink Through a break in the skin

3. Droplet Infection When you cough, sneeze or talk, tiny droplets full of pathogens are expelled into the air. Other people breathe these in. E.g. Tuberculosis, Influenze, Common Cold 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

4. Direct Contact Some diseases spread by direct contact of the skin. e.g. Impetigo, Genital Herpes 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2.How does your body stop pathogens getting in?

5. Contaminated Food and Drink Eating raw or undercooked food, or drinking water containing sewage can spread disease. E.g. Salmonella, Cholera 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

6. Through a Break in the Skin Pathogens can enter the body through cuts, scratches and needle punctures E.g. HIV, Hepatitis 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

7. Task 1 Describe the four main ways in which infectious diseases are spread. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

8. Preventing Microbes Getting In There are three main barriers to infection. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2.How does your body stop pathogens getting in? The Skin Scabbing Mucus and Stomach Acid

9. Preventing Microbes Getting In The skin prevents bacteria and viruses from getting to your tissues underneath. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

10. Preventing Microbes Getting In If you cut your skin, you bleed. Your blood quickly clots and forms a scab. This prevents any pathogens from entering. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

11. Preventing Microbes Getting In When you breathe, you draw in air full of pathogens. Your breathing system produces mucus which traps them. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in?

12. Preventing Microbes Getting In The mucus can then be removed from the body (blowing your nose) or swallowed into the gut, where stomach acid destroys the pathogens. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2.How does your body stop pathogens getting in?

13. Task 2 Copy and complete the following table 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2.How does your body stop pathogens getting in? BarrierHow it protects against infection Skin Scabbing Mucus and Stomach Acid

14. Some pathogens still get through the barriers to infection. The body however has a second line of defence - the white blood cells of the immune system. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in? How White Blood Cells Protect Against Disease

15. White blood cells protect fight pathogens in three main ways. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in? How White Blood Cells Protect Against Disease Ingesting Microorganisms Producing Antibodies Producing Antitoxins

16. Some white blood cells ingest (take in) pathogens, destroying them so they can’t make you ill. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in? Ingesting Microorganisms

17. Some white blood cells produce antibodies that bind to antigens on bacteria and viruses and destroy them. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in? Producing Antibodies

18. Once your white blood cells have made an antibody for a specific pathogen, if you get re- infected, these antibodies can be made very quickly. This is immunity. 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2. How does your body stop pathogens getting in? Producing Antibodies

19. Task 3 Explain how white blood cells work using combination of sentences and labelled diagrams. – Key words: Antibodies, antigens, antitoxins, 1. How are diseases spread? Defence Mechanisms 3. How do white blood cells protect us from disease? 2.How does your body stop pathogens getting in?