Question

Which of the following statements describes the lungs at the functional residual capacity?

A: Atmospheric, intra-alveolar, and intrapleural pressures
are all equal
B: The lungs tend to collapse due to their elastic
properties
C: The chest wall tends to collapse due to its elastic
properties
D: Both A and C are correct
E: All of the above are true

Answer 1

The lungs at the functional residual capacity tend to collapse due to their elastic properties, which is balanced by the outward force of the chest wall, maintaining the lungs at their resting volume. The correct statement is B.

Step-by-step explanation:

The statement that describes the lungs at the functional residual capacity (FRC) is B: The lungs tend to collapse due to their elastic properties. Functional residual capacity refers to the volume of air remaining in the lungs after a normal, passive exhalation. At this point, the elastic properties of the lung tissues cause them to recoil inward while the chest wall also has a natural tendency to expand outward. The chest wall does not collapse due to its elastic properties; rather, it exerts an opposite force. It is the balance between these forces that maintains the lungs at their resting volume. Atmospheric pressure and intra-alveolar pressure equalize at end expiration, but intrapleural pressure is still slightly negative compared to atmospheric pressure, helping keep the lungs inflated. This difference in pressure is called the transpulmonary pressure, which keeps the airways open.