Biology GCSE B2

infections are caused by microogranisms entering the body and reproducing. 

Microogranisms are microscopic and measured in nanometres(millionth of a milimetre)
 there are 3 types:

• virus (smallest)
• bacteria (middle)
• fungus (largest)

 Ideal conditions for these microbes are: warmth, nutrients and moisture. 

disease causing microogranisms are called pathogens. 

The effects and infection has on the body is called SYMPTOMS.

microogranisms enter the body --> quickly reproduce --> damage done to cells or toxins secreted by microbes --> symptoms of feeling ill.  

The toxins microogranisms produce breaks down material holding cells together allowing them to enter more deeply.

however most of the time we're not affected by microbes because 
- they don't all cause diseases
- we have physical barriers on our body

physical barriers:
skin - repairs itself quickly if damaged to stop wounds from getting infected
skin opening -->sweat- forms protective layer on skin& contains substances microbes can't grow in 
eyes-->tears-contains enzymes that kill bacteria
stomach-->hydrochloric acid - acid kills bacteria and stops them spreading