Defence Mechanisms Biology AQA GCSE
- 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
- Droplet Infection
- 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
- The mucus is moved out of the body or to the gut, and acids in the stomach destory the micro-organisms
- 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
- Ingesting Micro-organisms
- How they spread
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