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Slide 1

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Chapter 1
Causes Of Disease…read more

Slide 2

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1.1 Pathogens
Pathogen ­ organism that causes a disease
Microorganisms are mostly beneficial to us
Pathogens include: fungi, virus and bacteria
Transmission ­ pathogen is transferred from one individual to
To be a pathogen, a microorganism must:
Gain entry to the host
Colonise the tissues of the host
Resist the defences of the host
Cause damage to the host tissues…read more

Slide 3

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1.1 Pathogens
Pathogens normally get into the body by penetrating one of the
organism's interfaces
Interfaces of
the body
Digestive System Gas-Exchange System
Food and water may carry Many pathogens enter through
pathogens into the stomach and the gas-exchange surfaces.
intestines via the mouth. E.g. Influenza, Tuberculosis & Bronchitis
pathogens enter this way
E.g. Cholera, typhoid & dysentery pathogens
enter this way…read more

Slide 4

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1.1 Pathogens
To help prevent the entry of pathogens the body has a number of
natural defences, these include:
A mucous layer that covers the exchange surfaces and forms a thick
sticky barrier that is difficult to penetrate.
Production of enzymes that break down the pathogens.
Production of stomach acid, which kills microorganisms.…read more

Slide 5

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1.1 Pathogens
Pathogens affect the body in 2 main ways:
How pathogens
affect the
Producing Toxins Damaging Host Tissue
Bacterial pathogens produce Pathogens cause damage by
toxins, E.g. The cholera bacterium preventing tissues functioning
produces a toxin that leads to properly . Many pathogens break
excessive water loss from the lining down the membranes of the host
of the intestines. cells.…read more

Slide 6

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1.2 Data & Diseases
Incidence ­ number of cases
Epidemiology ­ the study of incidence and pattern of a disease with a
view to preventing and controlling it
A correlation occurs when a change in 1 or 2 variables is reflected on a
change in the other.…read more

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