What causes disease
The term "disease" is used when our bodies function in a less effiecient way. It refers to malfunction in our bodies that may have physical, mental or social aspects. Disease can be cause in a number of different ways.
- fungi (e.g tinea cause ringworm)
- bacterial (e.g mycobacteruim tuberculosis cause TB)
- viruses (e.g influenza xause flu)
Diseases caused by pathogens are called infectios diseases. Those that can be passed from person to person are called communicable disease.
Different types of disease
There are many different causes of disease, including:
- pathogenic organisms
- genetic diseases
- nutrient dificiencies
- lifestyle and working conditions
- social activities
- degenerative diseases
mircroorganisms as pathogens
For a mircoorgansim to be a pathogen it must:
- gain entry to the host
- colonise the host's tissues
- resist the defences that the host has
- cause damage to the tissues of the host
Infection occurs when a pathogen gets into the host tissues and colonises them. Disease occurs when the infection causes symptoms in the host. Pathogens usually gain entry to the host through somewhere that has contact with the outside environment.
How pathogens affect the body
Pathogens affect the body in 2 main ways:
- by damaging host tissues. Sometimes the sheer numvers of a pathogen cause damage to the area that it has infected. Viruses inhibit the production of DNA, RNA and the proteins in the cell that it occupies. Many pathogens damage the host cell membranes.
- by producing toxins. Most bacterial pathogens produce toxins. These are usually proteins that can affect the body in a variety of ways.
How a virus causes disease
Viruses cause disease by reproducing within a host cell. This occurs because viruses lack the chemical ability to produce themselves so rely on a host cell to do so. They:
- invade the host cell
- inject their genetic material into the cell
- the host cell is them made to reproduce that viruses again and again
- eventaully the cell burst releasing the new viruses into the body
How bacteria and fungi cause disease
Bacteria produce toxins that affect and damage the body. These can affect the pH of an area or cell which affect the production of enzymes.
Fungal fibres grow into the upper layer of the skin which cause inflammation and damage. This can also provide another route into the body for other pathogens and infections.