Defence mechanisms help the body protect itself against the entry of microorganismMicroscopic (too small to see) organisms, such as bacteria and viruses and communicable A disease that can be passed from one organism to another. diseases.
If a microorganism does enter, white blood cells will kill them.
Skin – a barrier to microorganisms.
Mucous membranes – present in the respiratory systemThe organ system where air is taken into and out of the body, and gas exchange happens. to trap microorganisms.
Blood clotting – stops blood escaping and prevents the entry of microorganisms where the skin has been damaged.
The entry of a microorganism may cause us to be sick while our body fights the infection.