When the respiratory system is mentioned,
people generally think of breathing, but breathing is
only one of the activities of the respiratory system.
The body cells need a continuous supply of oxygen for
the metabolic processes that are necessary to maintain
life. The respiratory system works with the circulatory
system to provide this oxygen and to remove the waste
products of metabolism. It also helps to regulate pH
of the blood.
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Respiration is the sequence of events that results in the
exchange of oxygen and carbon dioxide between the atmosphere
and the body cells. Every 3 to 5 seconds, nerve impulses stimulate
the breathing process, or ventilation, which moves air through
a series of passages into and out of the lungs. After this,
there is an exchange of gases between the lungs and the blood.
This is called external respiration. The blood transports
the gases to and from the tissue cells. The exchange of gases
between the blood and tissue cells is internal respiration.
Finally, the cells utilize the oxygen for their specific activities.
This is cellular metabolism, or cellular respiration. Together
these activities constitute respiration.
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