What primary function does pulmonary surfactant serve within the alveoli?
Solution
Correct Answer: Option A
- The primary function of pulmonary surfactant within the alveoli is to reduce alveolar surface tension.
- Surfactant is a complex mixture of lipids and proteins secreted by type II alveolar cells. It spreads along the inner surface of the alveoli, where it lowers the surface tension of the thin fluid layer lining the alveoli.
- This reduction in surface tension is crucial because it prevents alveolar collapse (atelectasis) during exhalation and helps maintain alveolar stability, allowing for efficient gas exchange.
- Without surfactant, the surface tension would be much higher, making it difficult for the alveoli to expand during inhalation and increasing the work of breathing.
- This is especially important in newborns, where surfactant deficiency leads to neonatal respiratory distress syndrome.
To clarify other options:
- Option 2: Surfactant does not increase alveolar capillary permeability; permeability changes are related to inflammation or injury.
- Option 3: Oxygen binding to hemoglobin occurs in red blood cells and is not facilitated by surfactant.
- Option 4: Mucus secretion is primarily the function of goblet cells in the airway epithelium, not related to surfactant.
Reference: Ganong’s Review of Medical Physiology, 26th Edition, Chapter 26: Pulmonary Ventilation and Gas Exchange, p. 421
- Surfactant is a complex mixture of lipids and proteins secreted by type II alveolar cells. It spreads along the inner surface of the alveoli, where it lowers the surface tension of the thin fluid layer lining the alveoli.
- This reduction in surface tension is crucial because it prevents alveolar collapse (atelectasis) during exhalation and helps maintain alveolar stability, allowing for efficient gas exchange.
- Without surfactant, the surface tension would be much higher, making it difficult for the alveoli to expand during inhalation and increasing the work of breathing.
- This is especially important in newborns, where surfactant deficiency leads to neonatal respiratory distress syndrome.
To clarify other options:
- Option 2: Surfactant does not increase alveolar capillary permeability; permeability changes are related to inflammation or injury.
- Option 3: Oxygen binding to hemoglobin occurs in red blood cells and is not facilitated by surfactant.
- Option 4: Mucus secretion is primarily the function of goblet cells in the airway epithelium, not related to surfactant.
Reference: Ganong’s Review of Medical Physiology, 26th Edition, Chapter 26: Pulmonary Ventilation and Gas Exchange, p. 421
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