Infectious diseases and body barriers

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  • Created by: alexda
  • Created on: 04-05-14 13:28
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  • Infectious Diseases
    • A pathogen is a microorganism that spreads disease.
    • Pathogens can spread in different ways:
      • 5. Body fluids
        • Some pathogens are spread by body fluids such as blood, breast milk and semen.
          • e.g. The HIV virus that causes AIDS is spread by body fluids.
      • 4. Contact
        • Pathogens can be pciked up by touching contaminated surfaces including the skin.
          • e.g. Athlete's foot is a fungus which makes skin itch and flake off. It is mostly spread by touching the same things as an infected person.
      • 6. Animal Vectors
        • Vectors are animals that spread disease.
          • e.g. Malaria is caused by an Anopheles mosquito which carries a protozoa. It spreads the disease bu biting other organisms.
          • e.g. Dysentery is causes by a House Fly which carries the bacterium. It spreads the disease by carrying the bacteria onto food.
      • 2. Food
        • Other pathogens can be picked up by eating contaminated food.
          • e.g. Salmonella bacteria cause food poisoning and are found in food that are kept too long or not cooked properly.
      • 1. Water
        • Some pathogens can be picked up by drinking or bathing in dirty water.
          • e.g. Cholera is a bacterial infection that causes diarrhoea and dehydration by contaminated water.
      • 3. Air
        • Airborne pathogens are carried in the air as in droplets produced when you cough or sneeze - so other people can breathe them in.
          • e.g. The influenza virus that causes flu.
      • There are four types of pathogens: bacteria, protozoa, fungi and viruses.
    • Physical and Chemical barriers stop pathogens entering the body.
      • 1. Undamaged skin is a effective barrier against microorganisms. If it get damaged blood clots quickly to seal cuts and keep microorganism out.
      • 1. Eyes produce a chemical called lysozyme in tears which kills bacteria on the surface of the eye.
      • 2. The respiratory tract is lined with mucus and cilia. The mucus catches dust and dirt before it reaches the lungs and the cilia push the mucus away from the lungs.
      • 2. If you eat food that contains pathogen most of them will be killed by the hydrochloric acid in your stomach.


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