Download Science Probe 5 Chapter 4.3 - P 92-95

apter 4
Ch
Your Respiratory System
and How It Works
왖 The air you breathe provides you with the oxygen you need.
As you read, connect
what you learn to your
own life. Ask yourself,
"How does oxygen help
keep me healthy?"
Your body needs nutrients and water to stay alive and healthy.
You also need one more thing—oxygen. Without oxygen, you
could only survive for a few minutes. Oxygen is a gas that is
found in the air you breathe. Just as a fire cannot burn without
oxygen, your cells cannot “burn” the fuel from the food you
eat without oxygen. Your body needs oxygen to release the
energy from the nutrients in your cells. Without oxygen, these
nutrients would not release energy, and all the systems in your
body would shut down.
How does your body get oxygen? This is the job of the
respiratory system. The main organs of the respiratory
system are the mouth, nose, trachea [TRAY-kee-uh], and
lungs. Let’s see how these organs work to bring oxygen to
your cells.
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Nose
Mouth
Trachea
Rib cage
Lungs
Diaphragm
왖 Your respiratory system brings oxygen to the cells in your body.
You breathe in air through your nose or your mouth.
Breathing in is called inhaling. The air travels down your
throat to a tube called the trachea. The trachea is also
called the windpipe. There is a flap over the trachea. This
flap opens when you are breathing in so air can go down to
your lungs. It closes if you are drinking or eating so that
food or liquid does not go down the trachea.
As you read, use your
finger to trace the parts
of the respiratory
system on the diagram.
The bottom of the trachea divides into two branches.
Each branch goes into a lung. A lung is a spongy organ
in your chest that sits inside your ribs. You have two lungs.
The branch in each lung divides into smaller and smaller
branches. At the end of these branches are tiny clusters of
air sacs. It is here that the oxygen in the air is picked up and
carried to all the cells in your body by your blood.
Just below your lungs is a muscle called the diaphragm
[DIE-uh-FRAHM]. This muscle moves up and down to help
you breathe.
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Getting Rid of Wastes
Your respiratory system has another job to do. Oxygen works
with the nutrients in your cells to produce energy. Producing
energy also produces water and carbon dioxide.
왖 Cells use oxygen and nutrients to produce energy. Water and carbon dioxide are also produced.
Water is very important to the cells in your body.
Sometimes, however, your cells don’t need all the water in
your body. The water that is left over needs to be removed
as waste. Some of the waste water is in the air you breathe
out. This is why your breath is moist.
왘 What happens when
you breathe on a mirror?
What does this show you
about your breath?
Carbon dioxide [KAR-buhn die-AWK-side] is a gas. It is
harmful to your body, so your body must remove it quickly.
Your blood picks up the carbon dioxide and takes it to your
lungs. You get rid of it when you breathe out. Breathing out
is called exhaling.
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How You Breathe
The diaphragm helps the air move in and out of your lungs.
When you breathe in, the diaphragm contracts and moves
down. Muscles are attached to the ribs. These muscles lift
your rib cage so it expands. When the rib cage expands,
air enters the lungs. When you breathe out, the diaphragm
relaxes and moves up. The muscles attached to your ribs also
relax. When the rib cage gets smaller, air leaves the lungs.
Breathing in
When you don't
understand a word, you
can often figure it out
by reading the words
around it. Read this
paragraph. What do
you think the word
"contract" means?
Breathing out
Rib cage
expands
Rib cage
gets smaller
Diaphragm contracts and moves down
Diaphragm relaxes and moves up
왖 Inhaling
왖 Exhaling
1. Why does your body need oxygen? How does your body get
this oxygen?
2. List two ways in which the air you breathe in is different from
the air you breathe out.
3. Describe how air gets into and out of your body.
NEL
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