What is disease?
- Certain symptoms caused by disease, either physical or mental.
- Malfunction of the body or mind which has an affect on good health.
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Microorganisms as pathogens
- Gain entry to the host
- Colonise the tissues of the host
- Resist the defences of the host cell
- Cause damge to the host
Pathogens include: Viruses, bacteria and fungi.
- If pathogens colonise a tissue it causes an infection
- A disease is caused when the infection leads to recognisable symptoms
- When the pathogen is trasferred from one individual to another is called transmission
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Entering the body
- They get into the body by penetrating the organisms interfaces with the environment
- An example of an interface is the skin, which forms a thick, continuous layer which acts as a barrier to infection
- The gas exchange system is also an interface, it has developed a mucus layer which is hard to penetrate
- The digestive system allows food and water, which may contain pathogens, to be consumed.
- The body produces enzymes to breakdown the pathogens and also produces stomach acid to kill microorganisms
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- Damaging host tissues: the large number of pathogens can cause the surrounding tissues to not function properly, inhibit the synthesis of DNA or breakdown the membrane of the cells.
- Produce toxins: produce toxins which are harmful to the surrounding tissues.
- Pathogens, lifestyle and genetic factors can all cause disease.
- The faster a pathogen divides, the faster it can cause disease.
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