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THE FIRST LINE OF
DEFENCE
How do we stop them getting in?
• The body has two barriers
against microorganisms
• There are physical barriers
like the skin and the hairs in
the nose
• The body also has chemical
barriers like the acid in the
stomach and a chemical in
the tears
The skin
• There are useful
microbes on the skin
• They compete with the
pathogens and stop
them getting food
• The skin is covered with
hairs which have oil
glands which produce a
chemical called sebum
that kills many microbes
The nose
• The hairs in the nose
keep out dust and
microorganisms
• The hairs are called cilia
and they move about
stopping the dirt and
microorganisms from
getting into your lungs
The stomach
• The lining of the stomach
has some special cells
which make hydrochloric
acid
• This kills any
microorganisms which get
into your body with your
food
The tears
• Your tears contain
a chemical called
lysozyme
• This kills microbes
on the surface of
your eyes
Now try this exercise
Exercise 5 - Crossword