Pathogens

Pathogens:
Include bacteria, virus and fungi.
Pathogens are micro-organisms that cause disease.
They cause disease by penetrating or going through one of the interfaces with the environment, e.g. skin, gas exchange system (mouth, nose, lungs are ideal for bacterial growth/culture), the digestive system (food and water carrying the pathogens in.)
Pathogens cause disease by either damaging host tissues (Number of pathogens causes damage, like preventing them from functioning properly, many pathogens can break down membranes, for example.) Or, by producing toxins, which most bacterial pathogens do, such as the cholera bacterium (vibiro cholorae) that leads to water loss for the intestines.

1) A pathogen is a micro-organism that causes disease
2) The digestive system and respiratory system is often a site of entry for pathogens, as they are richly supplied with blood vessels. Also, the body linings at these points are thin, moist (sticky) and have a large surface area. So, overall, Blood vessels, large surface area, thin, and moist (sticky.)
3) The two ways pathogens cause disease are through, firstly, causing damage to the host tissue. The sheer numbers of the pathogen could stop the cell from functioning properly, such as breaking down the membrane. And, secondly, by producing toxins, these could have an effect such as the cholera bacterium, which causes water loss in the lining of the intestines.
4) A reason why gastroenteritis/diarrhoea are not treated with oral antibiotics, is because the main symptoms are diarrhoea and vomiting, which would mean the antibiotic would be digested properly, and therefore, wouldn’t have the desired effect.