THE HUMAN RESPIRATORY SYSTEM AND BREATHING
Section I. THE RESPIRATORY SYSTEM
a. Respiration. Respiration is the exchange of gases between the atmosphere
and the cells of the body. It is a physiological process. There are two types of respira-
tion--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.
b. Breathing. Breathing is the process that moves air into and out of the lungs.
It is a mechanical process. 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, interaction
between the diaphragm and the abdominal wall causes the air to move into and out of
7-2. COMPONENTS AND SUBDIVISIONS OF THE HUMAN RESPIRATORY
See figure 7-1 for an illustration of the human respiratory system.
a. Components. The components of the human respiratory system consist of
air passageways and two lungs. Air moves from the outside of the body into tiny sacs in
the lungs called alveoli (pronounced al-VE-oh-lie).
b. Main Subdivisions. The main subdivisions of the respiratory system may be
identified by their relationship to the voice box or larynx. Thus, the main subdivisions