Breathing
Basic Lung Structure: (see pg. 286)
In order to bring gases into the lungs, a difference in air pressure is
created in the lungs.
Gases move from high pressure areas to low pressure areas.
Low pressure in the lungs will allow inspiration, high pressure allows
expiration.
To change the pressure in the lungs, the muscle called the
diaphragm is used to expand or shrink the lungs. (See Fig. 3 & 4 on
pg. 288)
Helping the diaphragm are the external and internal intercostals
muscles of the ribcage.
These muscles allow the ribs to move; this can help expand or shrink
the lungs.
An injury to the lungs (collapsed lung) can make it difficult to change
the pressure in the lungs, making breathing difficult.