Causes of Disease (Pathogens)

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  • Created on: 09-10-14 13:05
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Microorganism ­ single-celled organism (too small to be seen with a microscope)
Microorganisms live in our bodies often benefits us but sometimes causes harm
Microorganisms that cause disease Pathogens
Pathogenic microorganisms include:
Some bacteria
Some Fungi
All Viruses
Disease Malfunction of the body or mind which has an adverse effect on good health
Microorganism Pathogen it must:
Gain entry to the host
Colonise the tissues of the host
Resist the defences of the host
Cause damage to host tissues
When a pathogen gets into host and colonises its tissue = Infection
Disease = infection leading to recognised symptoms in the host
Pathogen transferred from one individual to another = transmission
Microorganisms getting into body:
Penetrating one of the organism's interfaces with the environment
Interface = surface or boundary linking two systems, linking the external environment
with the internal environment of the body
Skin ­ forms a thick continuous layer which is an effective barrier t infection
Invasion occurs when skin is broken or cut
Some interfaces have evolved allow exchange of material:
o Body linings are thin, moist and sticky
o Have a large surface area
o Well supplied with blood vessels
Makes it easy entry for pathogenic microorganisms

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Gas exchange system
Pathogens enter body that cause influenza, tuberculosis and bronchitis
Digestive system
Food and water enters the body through the mouth to the stomach
Cholera, typhoid and dysentery enter the body this way
Preventing entry:
o Mucous layer that covers exchange systems ­ forms sticky barrier
o Production of enzymes ­ breaks down pathogens
o Production of stomach ­ kills microorganisms
Damaging host tissues
o Sometimes the amount of pathogens causes damage ­ prevents tissues
functioning properly
o Viruses inhibit the synthesis…read more

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Main cause of mouth, throat and lung cancer
Excessive exposure to sunlight
o Skin cancer
o Using sunbeds and sunbathing without sunscreen increases risk
Excessive alcohol intake
o Increase risk of many cancers esp. liver cancer
How quickly pathogen causes damage onset of symptoms how rapidly the pathogen
o Pathogens divide every 30 minutes and symptoms become apparent in 24 hours of
infection.…read more


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