biology unit 4

biology chapter 4

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  • Created by: Amy
  • Created on: 19-02-12 19:59

B1A 4.2

Defence Mechanisms:

there are a number of ways we can spread pathogens from one person to another.The more pathogens you get inside your body, the more likely it is that you will get an infectious disease.

  • Droplet infection: when you cough,sneeze or talk you expel tiny droplets full of pathogens from your breathing system. other people breathe in the droplets along with the pathogens that they contain. so they pick up the infection. 
  • Direct contact: some diseases are spread by direct contact of the skin. 
  • contaminated food and drink: Eating raw or uncooked food, or drinking water containing sewage can spread diseases. 
  • Through a break in your skin: pathogens can enter your body through cuts, scratched and needle punctures. 
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Preventing microbes getting into your body:

Each day you come across millions of disease- causing microorganisms. your body has a number of ways of stopping these pathogens getting inside. 

  • your skin covers your body and acts as a barrier. it prevents bacteria and viruses from reaching the vulnerable tissue underneath.
  • if you damage or cut your skin in any way you bleed. platelets in your blood quickly help to form a clot which dries into a scab. the scab forms a seal over the cut, stopping pathogens getting in through the wound. 
  • your breathing system could be a weak link in your bodies defenses. your breathing organs produce mucus which traps the pathogens. 
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