1-7. COSTAL (THORACIC) BREATHING
a. Inhalation. Muscles attached to the thoracic cage raise the rib cage. A
typical rib might be compared to a bucket handle, attached at one end to the sternum
(breastbone) and at the other end to the vertebral column. The "bucket handle" is lifted
by the overall movement upward and outward of the rib cage. These movements
increase the thoracic diameters from right to left (transverse) and from front to back
(A-P). Thus, the intrathoracic volume increases. Recalling Boyle's law, the increase in
volume leads to a decrease in pressure. The air-pressure outside the body then forces
air into the lungs and inflates them.
b. Exhalation. The rib cage movements and pressure relationships are
reversed for exhalation. Thus, intrathoracic volume decreases. The intrathoracic
pressure increases and forces air outside the body.
1-8. DIAPHRAGMATIC (ABDOMINAL) BREATHING
The diaphragm is a thin, but strong, dome-shaped muscular membrane that
separates the abdominal and thoracic cavities. The abdominal wall is elastic in nature.
The abdominal cavity is filled with soft, watery tissues.
a. Inhalation. As the diaphragm contracts, the dome flattens and the
diaphragm descends. This increases the depth (vertical diameter) of the thoracic cavity
and thus increases its volume. This decreases air pressure within the thoracic cavity.
The greater air pressure outside the body then forces air into the lungs.
b. Exhalation. As the diaphragm relaxes, the elastic abdominal wall forces the
diaphragm back up by pushing the watery tissues of the abdomen against the underside
of the relaxed diaphragm. The dome extends upward. The process of inhalation is thus
Section III. CONDITIONS AFFECTING THE RESPIRATORY SYSTEM
Many conditions affect the respiratory system. Some of the conditions are life-
threatening, while many are chronic conditions which affect thousands of patients.
Many of the patients who suffer from these conditions will be standing in front of the
outpatient pharmacy in order to receive prescriptions to obtain some relief.
Pneumonia is caused by an infection of the lung. This infection is caused by
either bacteria (like the pneumococcus bacterium) or viruses. In pneumonia the walls of