Question

question 33
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without pulmonary surfactant, which of the following would happen?
the airway resistance would increase.
thoracic wall compliance would decrease.
intrapleural pressure would become zero.
the alveoli would collapse during expiration.

Explanation:

Pulmonary surfactant reduces surface tension in the alveoli. Without it, surface tension increases. This makes alveoli more likely to collapse during expiration (as per Laplace's law \(P = \frac{2T}{r}\), where \(P\) is pressure, \(T\) is surface tension, and \(r\) is radius; higher \(T\) leads to higher \(P\) promoting collapse). Airway resistance is related more to airway diameter (e.g., bronchoconstriction/dilation), thoracic wall compliance is about the chest wall's elasticity (not directly surfactant - related), and intrapleural pressure is negative due to lung recoil and chest wall expansion (not zero without surfactant).

Answer:

The alveoli would collapse during expiration.