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The Pulmonary System
Structure and Function
Lungs
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Lung tissue weighs 1 kg and
covers half a tennis court
(50-100 square feet)
Lung tissue is 20-50 times
larger than the body’s
external surface
Hold 4-6 liters of air.
Unattached to ribs;
suspended inside the pleural
sacs.
Function
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Ventilation. Breathing (air in
and air out)
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Conduction.
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Movement of air through the
pulmonary system
Respiration.
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Gas exchange (O2 and CO2)
Conduction Zone (humidify, filter)
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Nasal cavity and Pharynx
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Nose moistens, warms, and filters air;
mouth does not.
Larynx - voice box
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Epiglottis
Valsalva maneuver
Conduction Zone (humidify, filter)
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Trachea
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conducting tube (transports
air)
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Bronchi
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Branches
 contains muscle, serves to
dilate and constrict
Anatomic dead space
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Respiration
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Bronchioles
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further branching
Alveolar sacs (300 million)
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Each alveoli is surrounded by a
network or covering of
capillaries.
Almost forms a “sheet” of
blood.
At rest, a single blood cell
passes by 2 or 3 alveoli in about
0.5 to 1.0 seconds
Respiration (gas exchange)
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Occurs through thin
walls (0.3
micrometers)
Diffusion of gases
from high to low
concentration.
Types of Respiration

Pulmonary (external)
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Transfer of O2 and CO2 at the lungs.
250 mL of oxygen is exchanged per minute at rest
200 mL of CO2 is exchanged per minute at rest
These numbers can increase up to 25 times during
heavy exercise
Cellular (internal) respiration - transfer of O2
and CO2 in the tissues.
Mechanics of Breathing
Pleura
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Pair of membranes (inner and outer) surrounding
the lungs
Fluid in between two sacs provides the only
attachment of the lungs to the thorasic cavity (ribs).
Pleura
Pleura
Pneumothroax
Pressure
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Inspiration
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Air moves into the lungs
due to a lower pressure
inside the lungs
Expansion of the rib
cage and the lowering
of the diaphragm
increase the volume
As the volume gets
larger, the pressure
becomes lower.
Pressure

Expiration
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Air moves out of the lungs
due to a higher pressure
inside the lungs
Constriction of the rib cage
and the raising of the
diaphragm decrease the
volume
As the volume gets
smaller, the pressure
becomes higher.
Muscles of Ventilation
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Inspiration
Rest
 diaphragm and E.IC
muscles
Exercise
 pectorals, scalenes, SCM
Expiration
Rest
 no muscles
Exercise
 abs, I.IC. muscles)
Lungs and Exercise
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At rest, the blood is 97-98% saturated with
oxygen
Exercise, the blood remains 97-98%
saturated
Healthy lungs do not limit a person’s ability to
exercise
However, respiratory muscles need to be
trained like any other skeletal muscle