pathogen- what is disease?
- A 'micro-organism' is a single-celled organism that is too small to be seen without a microscope.
- micro-organisms include: bacteria and viruses.
what is meant by disease?
- disease suggests a malfunction of body or mind which has an adverse effect on good health.
For a micro-organism to be considered a pathogen it MUST:
- gain entry to the host,
- colonise the tissues of the host,
- resist the defences of the host
- cause damage to the hosts tissues
pathogens include: bacteria, fungi and viruses.
pathogens entering the body.
- If a pathogens enters the host and colonises its tissues then an infection results.
- Disease occurs when an infection leads to recognisable syptoms.
- When a pathogen is passed from one individual to another it is known as transmission.
How do micro-organisms enter the body?
micro-organisms enter the body through interfaces. (an interface is a surface or boundary linking to systems). Two types of interface are:
- the gas-exchange system. some pathogens that enter this way are: influenza, tuberculosis and bronchitis.
- the digestive system. Some pathogens that enter this way are: cholera and typhoid.
how does the body prevent pathogens from entering?
The body has a number of natural defences that prevent pathogens from entering these include:
- a mucous layer that covers exchange surfaces and forms a thick sticky barrier that is difficult to penetrate.
- the production of enzymes that break down pathogens.
- the production of stomach acid, which kills micro-organisms.
How do pathogens cause disease?
pathogens affect the body in two main ways:
- by damaging the host tissues.
- by producing toxins.