During inspiration, muscular contraction of the diaphragm causes air to move into the lung. The mechanism that drives air movement during inspiration results in a(n):
a. decrease in intra-alveolar pressure and shortening of the rib cage.
b. decrease in the size of the thorax and alveolar expansion.
c. increase in the size of the thorax and decrease in intrapleural pressure.
d. increase in atmospheric pressure and intrapleural pressure.
ANS: C
Inspiration occurs due to an increase in the size of the thorax and a decrease in intrapleural pres-sure, thus creating a negative pressure that draws air into the lungs. The rib cage lengthens, not shortens. The size of the thorax increases, not decreases. Intrapleural pressure decreases, not in-creases.
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