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Lesson 16
What is the respiratory system?
Almost every living thing must
take in oxygen in order to live.
Breathing is the process of
bringing air into the organism.
Breathing also gets rid of used
air.
As you have learned, breathing
is done by means of lungs. The
lungs, along with several other
organs, make up the respiratory
system.
The job of the respiratory system
is to take oxygen into the lungs
and to get rid of carbon dioxide
and water.
Here is the path air takes when
you inhale or exhale:
1- Air enters the body through
the mouth or nose
2. It moves into your throat and
passes through the windpipe, or
trachea.
3- The trachea branches into two
tubes called bronchi. Each
bronchus extends into one of the
lungs.
4- The lungs are the main
organs of the respiratory system.
In the lungs, the bronchi branch
into smaller and smaller tubes.
At the end of the smallest tubes
are tiny air sacs called alveoli.
Each lung contains millions of air
sacs.
Each air sac is surrounded by
capillaries.
While the air is in the air sacs,
two things happen:
1. Blood picks up oxygen
2. At the same time, the air sacs
take the carbon dioxide from the
blood.
When you exhale, you breathe
out the carbon dioxide. Some
waste water and heat are also
exhaled.