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Chapter 46
Section 3 The Respiratory System
Objectives
• Differentiate external respiration from internal
respiration.
• Trace the path of air from the atmosphere to the
bloodstream.
• Describe how gases are exchanged in the lungs and
transported in the bloodstream.
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Chapter 46
Section 3 The Respiratory System
Respiration
• The function of the respiratory system is to
exchange gases with the cardiovascular system.
• The respiratory system involves both external
respiration and internal respiration.
– External respiration is the exchange of gases
between the atmosphere and the blood.
– Internal respiration is the exchange of gases
between the blood and the cells of the body.
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Chapter 46
Section 3 The Respiratory System
The Human Respiratory System
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Chapter 46
Section 3 The Respiratory System
Parts of the Human Respiratory System
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Visual Concept
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Chapter 46
Section 3 The Respiratory System
The Lungs
• The lungs are the central organs of the
respiratory system in which gases are
exchanged.
• The lungs are located inside the thoracic cavity,
which is bound by the rib cage and the
diaphragm.
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Chapter 46
Section 3 The Respiratory System
The Lungs, continued
• The Path of Air
– External respiration begins at the mouth and at
the nose.
– Air is filtered & moved into the tube at the back
of the mouth called the pharynx (aka throat).
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Chapter 46
Section 3 The Respiratory System
The Lungs, continued
• The Path of Air, continued
– Air then moves past the from the epiglottis into
a cartilaginous tube, called the trachea.
• The epiglottis is a flap of cartilage that
hangs at the entrance of the larynx and
directs food and air to the correct places.
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Chapter 46
Section 3 The Respiratory System
The Lungs, continued
• The Path of Air, continued
– At the end of the trachea, the air moves into
the two bronchi and into the lungs.
– The air then moves into smaller tubes called
the bronchioles.
– Air then moves to the alveoli where gas
exchange takes place.
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Chapter 46
Section 3 The Respiratory System
Gas Exchange and Transport
• Gas Exchange in the Lungs
– Alveoli are surrounded by webs of
capillaries. The air passes from the alveoli
to the capillaries via diffusion to be
transported throughout the body.
– At the same time, carbon dioxide passes
from the capillaries to the alveoli via
diffusion to be exhaled as waste.
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Chapter 46
Section 3 The Respiratory System
Gas Exchange in the Lungs
QuickTime™ and a
Sorenson Video 3 decompressor
are needed to see this picture.
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Chapter 46
Section 3 The Respiratory System
Gas Exchange and Transport, continued
• Transport of Oxygen
– Most of the
oxygen absorbed
into the blood
combines with
hemoglobin, which
distributes the
blood to cells.
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Chapter 46
Section 3 The Respiratory System
Hemoglobin and the Transport of Oxygen
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Visual Concept
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Chapter 46
Section 3 The Respiratory System
Blood and the Transport of Carbon Dioxide
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Visual Concept
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Chapter 46
Section 3 The Respiratory System
Mechanism of Breathing
• Breathing is the process of moving air into and
out of the lungs.
• Inspiration is the process of taking air into the
lungs.
• When a deep breath is taken, the chest and ribs
expand.
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Chapter 46
Section 3 The Respiratory System
Mechanism of Breathing, continued
• Expiration is the process of releasing air from the
lungs. When this happens, the diaphragm and rib
muscles relax, which forces the lungs to
deflate.
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Chapter 46
Section 3 The Respiratory System
Inhalation and
Exhalation
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