Multiple Choice
Which is true about the pulmonary circuit as compared to the systemic circuit?
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22. The Respiratory System
Introduction to Lung Physiology
Multiple Choice
Why do the lungs expand as the rib cage lifts and the diaphragm contracts?
A
The diaphragm contraction increases the pressure inside the lungs, pushing air out.
B
The rib cage expansion compresses the lungs, forcing air out.
C
The contraction of the diaphragm directly pulls air into the lungs.
D
The increase in thoracic volume decreases the pressure inside the lungs, causing air to flow in.
Verified step by step guidance1
Understand the basic mechanics of breathing: Breathing involves changes in pressure and volume within the thoracic cavity, which houses the lungs.
Recognize the role of the diaphragm: The diaphragm is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. When it contracts, it moves downward, increasing the volume of the thoracic cavity.
Consider the rib cage movement: As the diaphragm contracts, the intercostal muscles between the ribs also contract, lifting the rib cage upward and outward, further increasing the thoracic volume.
Apply Boyle's Law: According to Boyle's Law, the pressure of a gas is inversely proportional to its volume. As the thoracic volume increases, the pressure inside the lungs decreases.
Understand air flow dynamics: With decreased pressure inside the lungs compared to the outside atmosphere, air flows into the lungs to equalize the pressure, facilitating inhalation.
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