b. However, during forced breathing, the muscles of the abdominal wall will
contract in accordance with the amount of air to be pushed out.
c. As the muscles in the abdominal wall rebound (and contract in forced
breathing), pressure is applied to the fluid continuum in the abdominopelvic cavity. By
Pascal's law, this pressure is transferred to the underside of the thoracic diaphragm.
The relaxed thoracic diaphragm is thus pushed up into the thoracic cavity. This
decreases the vertical diameter and the volume of the thoracic cavity. The decreased
volume results in increased pressure within the lungs (Boyle's law). Since the air
pressure in the lungs is relatively greater than the outside atmospheric pressure, air is
forced out through the respiratory passageways. (This is aided by the elastic rebound
of tissues in the thoracic cavity.)
Section V. INTRODUCTION TO THE HUMAN RESPIRATORY SYSTEM
The human respiratory system consists of a series of organs that form a
passageway for the air flowing to and from the alveoli of the lungs. The lungs
themselves are discrete organs of the body containing the alveoli and are located in
individual serous cavities.
The air passageway can be conveniently divided into three groups of structures.
The larynx is the central portion. The other organs are grouped as supra laryngeal or
Section VI. THE SUPRALARYNGEAL STRUCTURES
7-20. GENERAL FUNCTIONS
The general functions of the supra laryngeal structures (Figure 7-3) are to
condition the in flowing air and to test it. Conditioning includes cleansing, warming, and