1.1 Pathogens

1.1 Pathogens

1. Micro-organisms that cause disease, e.g.viruses and bacteria

   • A microorganism is a single celled organism too small to be seen without a microscope
   • Disease is a description of certain symptoms - physical or mental. It suggests a malfunction of body or mind which has an adverse affect on good health
   • For a microorganism 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 host tissues

2. How pathogens enter the body:

   • the gas exchange system
   • The digestive system

3. The Body's defences against pathogens:

   • mucous layer that covers exchange surfaces and forms a sticky, hard to penetrate barrier
   • the production of enzymes that break down pathogens
   • production of stomach acid that kills microorganisms

4. How pathogens cause disease

   • By damaging host tissues
   • by producing toxins