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Section Objective
15-1
The Respiratory System
To describe the::s~~
tru:ctu~~~a
~~res :n:d~~::::::::::::::::::~;:~~~====~::::::::J
function of the respiratory
Try this: Breathe i'~. Easy, right? Now breathe
system
out. Again, no problem. You can breathe in or out
whenever you think about it. But what about when
you are asleep? When you sleep, you do not have I
worry that your body will not breathe. You breath(
automatically. But why breathe at all?
In Chapter 13, you learned that the diges tive
system breaks down food into s.!llaU molecules that
are transported by the blood' to your body cells. In
Chapter 14, you read how oxygen is carried by tht
blood to body cells. In the cells, the oxygen is com
bined with food to produce energy that the body
can use. This process is called respiration. You rna
also recall that the waste carbon dioxide is product
during respiration.
The job of getting oxygen int~ the body and
removing carbon dioxide and water is the ~ain
task of the respiratory system. This happens auto­
matically when you breathe. Breathing in and
breathing out are the first and last steps in the
Figure 15-1 The main job of the
process of respiration.
respiratory system is to get oxygen
into the body. Once inside the
body, the oxygen combines with
food to produce energy. This
energy enables you to perform
many activities, such as playing
volleyball. What is the process
called that combines oxygen with
food?
Nostrils
Throat - - - ----'
Bronchus -----::
338
The Nose and Throat
All the air that you use to breathe, sing, speak,
or shout is usually first taken into the respiratory
system through openings in the nose. These open-
~m
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when
lave to
eathe
lve
that
ls. In
y the
com­
)dy
nd
lin
auto-
,eak,
ory
'pen­
ings are called nostrils. If the air is cold, as it may
be in winter, it is quickly heated by warm blood that
flows through vessels near the inner lining of the
nose. Meanwhile, mucus in the nose moistens the
air. This keeps the delicate tissues of the respiratory
system from drying out. In addition, large hairs and
tiny hairs in the nose trap dust particles and micro­
scopic organisms such as bacteria and keep them
from going any farther into the respiratory system.
If the nose becomes irritated by these trapped parti­
cles, your body responds by producing a little "ex­
plosion" to force the particles out. As you may have
guessed, this explosion is a sneeze!
Because the nose warms, moistens, and filters the
air coming into the body, it is healthier to take in
air through the nose than through the mouth. But
when the nose is blocked, such as when you have a
cold, the mouth acts as a backup organ so that you
can continue breathing.
From the nose, the moist, clean air moves into
your throat. The air will cgme to a kind of fork in
the road. One path leads to the digestive system.
The other path leads deeper into the respiratory
system. What directs the air down the respiratory
path and objects such as food and water down the
digestive path? The "traffic" is routed down the
right path by a small flap of tissue called the
epiglottis. The epiglottis cuts off the opening to
your windpipe when you swallow and routes all food and water down to your digestive system.
The Trachea
Figure 15-2 In order to shout
cheers, these cheerleaders must
control the flo:;" of air through their
respiratory systems .
Figure 15-3 In the drawing, you
can see the position of the vocal
cords at the top of the trachea.
How are sounds produced by the
vocal cords?
Vocal cords
Take a moment to gently run your finger up
and down the front of your neck. You will feel al­
ternating bands, or rings, of cartilage and smooth
muscle. These rings form the protective wall of your
trachea (TRAy-kee-uh), or windpipe. If the epiglottis
is open, air passes from your throat into the tra­
chea. As the air moves downward, tiny hairs lining
the trachea trap dirt particles and bacteria that have
managed to get through the nose. Like the nose, the
trachea produces tiny explosions in response to irri­
tations. These explosions are calle9 coughs. During
a cough, air is sometimes forced Qut of the trachea
at speeds of up to 160 kilometer,s" per hour!
339
Figure 15-4 The long, brown­
colored object in this photograph
is a dirt particle trapped in the tiny
hairs in the bronchus . These hairs
move constantly, carrying the dirt
particle up through the windpipe to
the throat where it is coughed out
or swallowed. What is another
name for the windpipe?
Located at the top of the trachea is the larynx
(LAR-ihngks), or voice box. The larynx is made of '-'
cartilage. Within the lining of ,t he larynx are folds of
tissue called vocal cords. As air passes out and past
the vocal cords, they vibrate. These vibrations, to­
gether with the movements of the mouth and
tongue, produce sounds.
HELP WANTED: RESPIRATORY THER­
APY TECHNICIAN Completion of a one­
year program in respiratory therapy, taken
either at a hospital or technical school.
Certification as a respiratory therapy tech­
nician (CRrr) is desirable. A strong desire
to work with people is needed. Apply at
the hospital personnel office .
Somewhere each day tragic events occur,
such as drowning, drug poisoning, heart failure,
stroke, head injury, or electrical shock that can
cause a person t o stop breathing. It is vital that
the person be treated immediately for breathing
problems. That is th e job of the respiratory
.therapy technician.
In addition to working in emergency situa­
tions, t hese tech nicians work under the direc­
tion of doctors. With special equipment, the
technicians help people with respiratory dis­
orders such as asthma, emphysema, pneumo­
nia, and bronchitis. Some respiratory therapy
340
technicians work in laboratorie$ where they
measure lung volumes or give radioactive gas
to patients . The radioactive gas leaves a "trail"
that shows up on X-rays. This helps the doctor
in determining whether the re is a respiratory
problem and, if so, its degree of seriousness .
For more info rmation about this exciting and
challengi ng field. Write to the American Associ­
ation for Respiratory Therapy, 1720 Regal Row,
Dallas, TX 75235.
The Respiratory Tree
As you breathe, air passes down the throat and
into the trachea. Soon the air reaches a place where
the trachea branches into two tubes. Each of these
tubes is called a bronchus (BRAHNG-kuhs; plural:
bronchi). Each bronchus continues to branch into
smaller and smaller tubes. The bronchi and their
many smaller branches are often described as form­
ing an upside-down tree-the respiratory tree. See
Figure 15-5.
The thinnest branches of the respiratory tree
lead to grapelike clusters of tiny "balloons" called
alveoli (al-vEE-uh-ligh; singular: alveolus). The alve­
oli make up most 'of the tissue of the lungs, the
main organs of respiration. It is the alveoli that
make the lungs soft and spongy. Because of the hol­
low alveoli, your lungs are so light that they could
float. Each thin-walled alveolus is surrounded by a
network of capillaries. It is here that your blood
picks up its cargo of oxygen from the air. Oxygen
.,.
Figure 15-5 Notice how the
trachea , bronchi, smaller branches
of the bronchi, and alveoli form a
respiratory tree .
Figure 15-6 In this drawing, you
can see how oxygen and carbon
dioxide are exchanged in the
lungs. Where in the lungs does the
exchange of these gases occur?
Air passage
Blood high in
carbon dioxide
Trachea
Blood high
in oxygen
to body
. 1
I
Capillaries
i
~.:.::;:g t--Capillary
Smaller
branches
of bronchus
Carbon dioxide
diffUSing Into - - - \ - ';'I
alveolus
Red blood cells- - - - '
~B--'+f---O xygen
wall
from air
diffusing
into blood
I
from the alveoli passes into the blood flowing in th
capillaries. Afterward, the oxygen-rich blood will h
pumped back to the heart and sent through the ar
teries to all the tissues of the body. Meanwhile, the
waste gas carbon dioxide passes from the blood int
the alveoli. Within seconds, you breathe out the
waste gas carbon dioxide.
Mechanics of Breathing
Figure 15-7 The capillaries that
surround each alveolus are so tiny
that red blood cells must squeeze
through one at a time. What gas is
picked up by the red blood cells in
the alveoli?
Look down at your chest as you breathe in and
out. What do you see? As you taIse in a breath, you
chest expands. As you let the air_ out, your chest
becomes smaller. Why?
"
You may be quick to reply that air rushing into
your lungs makes your chest expand. And that air
rushing out makes your chest shrink. But that is no
the way it happens at all . Something else happens
first, before the air moves in"either direction. That
something has to do with some sets of muscles in
your chest. Here is how they work.
When you are about to take a breath, muscles
attached to your ribs contract and pull upward and
outward. At the bottom of your chest, a muscle
called the diaphragm (DIGH-uh-fram) contracts and
pulls down the bottom of your chest. Both of these
actions make the chest expand. Suddeqly there is
more space in it.
When your chest expands, there is more room
for air in your lungs. So the same amount of air is
in a larger space. This causes the air pressure in
your lungs to decrease. As a result, the air pressure
in your lungs becomes lower than the air pressure
outside your body. The difference in pressure
INHALATION
Figure 15-8 As the diaphragm
contracts (left), air pressure
decreases in the chest, causing
the lungs to inflate . When the
diaphragm relaxes (right), air
pressure increases in the chest,
causing the lungs to deflate. What
is this process called?
EXHALATION
tTi-:,..----"--
Lu n9
a.+-'Iri--- Rib
cage
'!~.J~~~M+--Diaphrag rr:t
342
· the
1 be
ar­
the
into tnd
forces air to rush into your lungs. That is why your
chest must expand before you inhale, or breathe in .
The reverse happens when you breathe out, -or
exhale. Your chest muscles relax. The space in your
chest becomes smaller. The air pressure becomes
greater inside than outside. The result? Air rushes
out of your lungs as it would out of a squeezed bal­
loon. How many breaths do you take in one minute?
SECTION REVIEW
1. What are the structures and function of the respi­
nto
air
.s not
:ns
'hat
ratory system?
2. What is respiration?
3. In which part of the lungs does the exchange of
oxygen and carbon dioxide take place?
4. Explain why you should not talk while you are
eating.
Sharpen Your Skills
What Is in Exhaled Air?
In the presence of carbon
dioxide, bromthymol blue so­
lution turns green or yellow.
1. Fill two test tubes with
10 mL of water and a few
drops of bromthymol blue
solution.
2. Label the tubes A and 8.
3. Using a straw, gently
blow air into the liquid in test
tube A.
4. Compare .the' test tubes.
What happened to the test
tubes? Explain. What was the
purpose of test tube 8?
In
.es and
and
hese
IS om
.ir is
In
ssure
,ure
15-2 The Excretory System-,....--=
The lungs, as you just learned, are part of the
respiratory system. But did you know that they are
also part of the excretory (EHKs-kruh-tor-ee)
system?
The job of the excretory system is to remove
various wastes produced by the body. The removal
process is known as excretion. Because the lungs
remove carbon dioxide and water, they are consid­
ered organs of excretion as well as organs of respi­
ration. Of course, excretion does not refer simply to
removing carbon dioxide. Excretion includes the
removal of excess water, salts, and certain nitrogen
wastes . Nitrogen wastes are produced when excess
amino acids , which are the building blocks of pro­
teins, are broken down in the body. Nitrogen
wastes, as you might expect, contain the element ni­
trogen. Excretion also includes the removal of drugs
and certain poisons that are taken into the body and
absorbed by the blood.
Although you probably do not often .think about
it, excretion is just as important to your body as
breathing and eating. During certain activities, the
body produces toxic (TAHK-sihk), or poisonous,
Section Objective
To describe the structures and
function of the excretory
system
Figure 15-9 In the skin , wastes
are excreted through tiny openings
called pores. The green circular
objects in this pore are bacteria.
What are some wa stes that are
excreted through the pores?