Download Respiration and Circulation The Respiratory System Functions of the Respiratory System

Respiration and Circulation
The Respiratory System
Functions of the Respiratory System
If you have ever held your breath, you probably took
deep breaths afterward. Those breaths were your body’s way
of getting the oxygen it needs. Breathing is the movement of air
into and out of the lungs. Breathing is how your respiratory
system takes in oxygen and gets rid of carbon dioxide.
Taking in Oxygen
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Think about the plumbing pipes that bring water into a
house. Your respiratory system is similar. It is a system of
organs that bring oxygen into your body. Oxygen is
important for life. In fact, your brain will tell your body to
breathe even if you try not to breathe. Your brain responds
when your body needs oxygen.
Why is oxygen so important? Every cell in your body needs
oxygen for cellular respiration. Cellular respiration is a series
of chemical reactions. During cellular respiration, oxygen and
sugars react. This reaction releases energy that a cell can use.
Eliminating Carbon Dioxide
A house’s plumbing pipes also remove wastewater. In a
similar way, your respiratory system removes waste gases
from your body. Carbon dioxide is one of the waste gases
that your respiratory system removes. If waste gases are not
removed, cells cannot function.
Organs of the Respiratory System
The figure below shows air moving into and out of the
respiratory system. Air enters your respiratory system
through your mouth and nose. Your nose warms and
moistens the air. Hairs and sticky mucus in your nose help
trap dust and dirt from the air.
Cilia are hairlike structures that line your nose and most
other airways in your respiratory system. Wavelike motions
of the cilia carry trapped particles away from your lungs. The
cilia help keep harmful particles from getting very far into
your respiratory system.
Nose
Mouth
Pharynx
Larynx
Trachea
Bronchi
Lungs
Pharynx
After air enters your mouth and nose, it passes into your
throat. The pharynx (FER ingks) is a tubelike passageway at the top
of your throat that receives air, food, and liquids from your mouth or
nose. The epiglottis (eh puh GLAH tus) is a flap of tissue at
the bottom of the pharynx. It keeps food and liquids out of
the rest of your respiratory system.
Larynx and Trachea
Air passes from your pharynx into a triangle-shaped area called the
voice box, or larynx (LER ingks). Your vocal cords are in your
larynx. They consist of two thick folds of tissue. Your vocal
cords vibrate and make sounds as air passes over them.
Air moves from your larynx into your trachea
(TRAY kee uh). Your trachea is a tube that is held open by
C-shaped rings of cartilage.
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Diaphragm
Bronchi and Lungs
Your trachea branches into two narrower tubes called bronchi
(BRAHN ki) (singular, bronchus) that lead into your lungs. Lungs are
the main organs of the respiratory system. Inside your lungs, your
bronchi branch into smaller and narrower tubes called
bronchioles.
Alveoli
In your lungs, your bronchioles end in microscopic sacs, or
pouches, called alveoli (al VEE uh li) (singular, alveolus), where gas
exchange occurs. During gas exchange, oxygen from the air
you breathe moves into your blood. Carbon dioxide from
your blood moves into your alveoli.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Look at the alveoli in the figure below. Alveoli look like
bunches of grapes at the ends of the bronchioles. Like tiny
balloons, your alveoli fill with air when you breathe in. They
contract and release air when you breathe out. Notice in the
figure below that blood vessels surround each alveolus. The
walls of alveoli are only one cell thick. Red blood cells drop
off carbon dioxide and pick up oxygen as they move
through these blood vessels.
The thin walls of alveoli and the large surface areas make
it possible for a high rate of gas exchange. If you could
spread out all the alveoli in your lungs onto a flat surface,
they would cover an area bigger than your classroom. Every
time you breathe, alveoli help your body take in billions of
oxygen molecules. They also help your body get rid of
billions of carbon dioxide molecules.
Wall of
alveolus
Oxygen
Carbon
dioxide
Alveoli
Lung
Red blood
cells
Gas exchange in alveoli
Blood
vessel
Breathing and Air Pressure
How does your body know when to breathe? When high
levels of carbon dioxide build up in your blood, your nervous
system tells your body to breathe out, or exhale. After you
exhale, you breathe in, or inhale. How does this happen?
Below your lungs is a large muscle called a diaphragm
(DI uh fram) that contracts and relaxes and moves air in and out of
your lungs. Air moves into and out of your lungs with the
help of your diaphragm. When your diaphragm moves, it
changes the air pressure inside your chest. Breathing occurs
because of these changes in air pressure.
When you inhale, your diaphragm contracts and moves
down, as shown below. The space around your lungs gets
bigger, or expands. The increased space reduces the air pressure
in your chest. Air rushes into your lungs until the pressure
inside your chest equals the air pressure outside it.
When you exhale, your diaphragm relaxes and moves
up. The space around your lungs gets smaller, or reduces.
Air pressure in your chest increases. Waste gases rush out
of your lungs.
Inhalation
Lung
Ribs
Lung
Ribs
Diaphragm
Exhalation
Respiratory Health
Have you ever had a cold, allergies, or asthma? If you
have, you know what it is like to have a respiratory illness.
You might have had a sore throat or a stuffed-up head that
made breathing uncomfortable. Some respiratory illnesses
make it hard to breathe. Serious respiratory illnesses can
even cause death.
The best way to maintain good respiratory health is to
stay away from irritants and air pollution. Common
respiratory illnesses and their causes are listed in the table
on the next page.
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Diaphragm
Respiratory Illnesses
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Illness
Causes
Symptoms
Colds, flu
viruses
congestion, runny
nose, watery eyes,
coughing, sneezing
Bronchitis
(brahn KI tus)
viruses, bacteria
coughing and tiredness resulting from
mucus blocking the
bronchi and bronchioles, slowing air
movement
Pneumonia
(noo MOH nyuh)
viruses, bacteria
trouble breathing as
a result of fluid in the
alveoli that slows gas
exchange
Asthma (AZ muh)
dust, smoke, pollen,
pollution
trouble breathing as
a result of swollen airways and increased
mucus
Emphysema
(em fuh SEE muh)
smoking
coughing, tiredness,
loss of appetite, and
weight loss resulting
from destruction of
alveoli
Lung cancer
smoking
coughing, trouble
breathing, chest pain
The Respiratory System
and Homeostasis
You have read in this lesson that the muscular system
works with your respiratory system so you can breathe. The
muscles and respiratory system working together bring oxygen
into your lungs and remove carbon dioxide from your lungs.
In the next lesson, you will learn how the circulatory
system and the respiratory system work together to bring
oxygen to body cells. These systems also work to remove
carbon dioxide from cells. The muscular system, the
respiratory system, and the circulatory system help maintain
homeostasis in your body.