Entry Routes of Pathogens
- In order for pathogens to cause disease they need to enter the body
- There are four main ways in which pathogens can enter
- Broken skin
- This provides direct access to the tissues and bloodstream
- The digestive system
- When we consume contaminated food and drink
- The respiratory system
- Every time we inhale
- Mucosal surfaces
- The lining of body cavities e.g. inside of nose, mouth, genitals
- Broken skin
Barriers to infection
- Skin
- This provides a physical barrier against infection
- If the skin is damaged it leaves the exposed tissue beneath vulnerable to pathogens
- The blood clotting mechanism of the body plays an important role in preventing pathogen entry in the case of damage to the skin
- Blood clotting takes time, however, so a few pathogens may still enter before a clot forms
- Microorganisms of the gut and skin
- Collectively these harmless microorganisms are known as the gut or skin flora
- They compete with pathogens for resources, thereby limiting their numbers and therefore their ability to infect the body
- Stomach acid
- The hydrochloric acid that makes up a large part of the gastric juices in the stomach creates an acidic environment that is unfavourable to many pathogens present on food and drink
- Sometimes a few of these pathogens may survive and make their way to the intestines where they infect the gut wall cells and cause disease
- Lysozyme
- Secretions of the mucosal surfaces, e.g. tears, saliva, and mucus, contains an enzyme called lysozyme
- This enzyme will damage bacterial cell walls, causing them to burst, or lyse
The body has physical defences that prevent the entry of pathogens
