Defence Mechanisms Biology AQA GCSE

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  • Created by: Caitlinyx
  • Created on: 22-04-13 17:51
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  • Defence Mechanisms
    • How they spread
      • Droplet Infection
        • When you cough, sneeze or talk, tiny droplets full of pathogens are expelled
        • Other people breathe in the droplets
        • Pick up infections like influenza, tuburculosis or the common cold
      • Direct Contact
        • Diseases can be spread through contact of the skin
        • For example impetigo and some sexually transmitted diseases like geniatl herpes
      • Contaminated food and drink
        • Eating raw or uncooked food
        • Drinking contaminated water
        • For example diarrhoea or salmonellosis
      • Through a break in the skin
        • Pathogens can enter your body through cuts, scratches or needle punctures
        • For example HIV/AIDs and hepititus
      • Crowded conditions spread disease quicker
    • Preventing microbes from entering the body
      • Skin covers the body and acts as a barrier. It stops the pathogens from reaching the tissue below
      • If you damage or cut your skin, it bleeds. The blood seals as a clot and forms a scab, stopping pathogens getting into the wound
      • Your breathing system produces a sticking liquid called mucus which covers the lungs and tubes and traps the pathogens.
        • The mucus is moved out of the body or to the gut, and acids in the stomach destory the micro-organisms
          • Did you know? Mucus from your nose turns green when you  have a cold because white blood cells contain green coloured enzymes, and dead white blood cells, along wiith the bacteria or virus cells, come out in the mucus, making it look green
    • White Blood Cells
      • Ingesting Micro-organisms
        • Some white blood cells ingest (take in), destroying them so you don't get ill
      • Producing Antibodies
        • Some white blood cells release chemicals called antibodies which target particular pathogens and destroy them.
        • There is a different antibody for each type of pathogen
        • Once your body has produced the antibodies once, the next time is a lot faster
      • Producing Antitoxins
        • Some white blood cells produce antitoxins which counteract (cancel out) the toxins released by pathogens


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