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Unit 19: Biology Part 2 Page 85 of 137
clear your throat or blow your The Second Line of
nose, the mucus and pathogens Defense
leave your body.
As good as the skin is at protecting
against infection, sometimes
pathogens do manage to get past
it. One common way for
pathogens to enter is through cuts
and scrapes. When the skin has
been cut, pathogens have an easy
point of entry.
If pathogens get through the skin,
and cause an infection, they will
Figure 73 – Under high face the body’s second line of
magnification, you can see that defense. For example, there might
the cilia of the nose look sort of be an inflammation in the area of
like a brush, sweeping away the infection. An inflammation
mucus and pathogens. happens when chemicals are
released causing the blood vessels
Things that come out of your body in the area to get larger, or dilate.
are called body secretions, and The area around the infection
many of these secretions can also becomes red, warm, and painful,
help protect you from disease. while blood flow to the area
Mucus, sweat, tears, and saliva all increases.
have chemicals called lysozymes.
Lysozymes are enzymes that kill
pathogens. The stomach secretes
a strong acid called hydrochloric
acid, which kills most pathogens in
food and water. Finally, very few
pathogens can grow in urine
because it is acidic.
Figure 74 – Although they can
be painful, inflammations help
the skin to heal.
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