Flashcards in 1. Causes Of Disease Deck (15):
A single called organism which is too small to be seen without a microscope.
For a microorganism to be considered a pathogen it must...
Gain entry to the host
Colonise host tissues (infection)
Resist the defences of the host
Cause damage to the host tissues
When a pathogen is transferred from one individual to another
Common points of entry for pathogens are...
The gas exchange system (surfaces) e.g influenza, tuberculosis and bronchitis.
The digestive system. (Food and water, into the stomach and intestines via the mouth) e.g Cholera, typhoid and dysentery
To prevent entry of pathogens the body has a number of natural defences...
A mucous layer that covers exchange surfaces and forms a thick sticky barrier which is difficult to penetrate.
The production of enzymes which break down the pathogens.
The production of stomach acid, which kills microorganisms.
Pathogens affect the body in two main ways:
By damaging host tissues (the sheer number of pathogens causes damage e.g by preventing tissues from functioning properly) (inhibiting DNA synthesis and breaking down host cell membranes).
By producing toxins e.g the cholera bacterium produces a toxin that leads to excessive water loss from the intestine lining.
What factors can cause disease?
Pathogens, lifestyle and genetic factors.
What is a pathogen?
A microorganism that causes disease.
Why are the digestive systems often the sites of entry for pathogens?
Diffusion takes place in these systems so they have a large surface area, are thin, moist and well supplied with blood vessels. This makes it easy for pathogens to attach to and penetrate them.
Why are oral antibiotics not used to treat diarrhoea.
Because they do not stay in the digestive system long enough to be absorbed.
A correlation but not a causal relationship.
The data seems to suggest that this is the case but there is no actual evidence to prove it. (To prove you would need experimental evidence to show that the variable led directly to the issue).
What is risk?
A measure of the probability that damage to health will occur as a result of a given hazard.
Factors which increase/decrease risk...
Stress levels, alcohol intake, occupation, gender, pollution, age, genetics
Lifestyle factors which contribute to cancer: