THE RESPIRATORY SYSTEM
a. The cells of the body require a constant supply of oxygen to carry on the
chemical processes necessary to life. As a result of these processes, carbon dioxide (a
waste product) is formed and must be removed from the body so that the cells do not
become poisoned by their own wastes. Oxygen and carbon dioxide are continuously
being exchanged, both between the body and the atmosphere and within the body, by
the physiological process known as respiration. The system that performs the
exchange of gases between the body and the atmosphere is the respiratory system.
b. There are two types of respiration--external and internal. External respiration
is the exchange of gases between the air in the lungs and blood. Internal respiration is
the exchange of gases between the blood and the individual cells of the body.
c. Breathing is the mechanical process that moves air into and out of the lungs.
There are two types of breathing in humans--costal (thoracic) and diaphragmatic
(abdominal). In costal breathing, the major structure causing the movement of the air is
the rib cage. In diaphragmatic breathing, the diaphragm causes the air to move into
and out of the lungs.
COMPONENTS AND SUBDIVISIONS OF THE RESPIRATORY SYSTEM
a. Components. The human respiratory system consists of air passageways
and two lungs (figure 1-1). Air moves from the outside of the body through the air
passages into tiny sacs in the lungs called alveoli.
b. Main Subdivisions. The main subdivisions of the respiratory system may be
identified by their relationship to the voice box (larynx). Thus, the main subdivisions are
(1) Supralaryngeal (above the larynx) structures. These structures include
the external nose, nasal chambers, and pharynx. These structures cleanse, warm,
moisten, and test inflowing air.
(2) Larynx (voice box). This structure controls the volume of inflowing air
and produces selected pitch (vibration frequency) in the moving column of air.
(3) Infralaryngeal (below the larynx) structures. These structures include
the trachea, bronchi, alveoli, lungs, and pleural cavities. They distribute air to the alveoli
of the lungs where the actual external respiration takes place.