Copy and complete these sentences.
A microorganism that can make a person ill is called a
. Some types of bacteria,
and
are pathogens. Some pathogens can get into the body
in food and drink. The stomach produces .
which helps to destroy these.
The skin has a thick layer of
that stops most pathogens getting into it. However,
if the skin is cut, pathogens may enter the blood. Blood helps to prevent this.
Many of the pathogens that are present in the air that we breathe in are prevented from reaching
the lungs, because they are trapped by sticky in the respiratory passages.