Question

What is the primary function of pulmonary surfactant?

• A. Facilitates gas exchange
• B. Increases surface tension in alveoli
• C. Prevents alveolar collapse
• D. Promotes mucociliary clearance

Hint:

Surfactant reduces surface tension — without it, alveoli collapse leading to respiratory distress syndrome.

Answer 1

The Correct Option is C

Step 1: Understanding Pulmonary Surfactant.
Pulmonary surfactant is a phospholipid-rich substance secreted by type II pneumocytes.
It lines the inner surface of alveoli.
Step 2: Role in Surface Tension.
Alveoli are lined by a thin fluid layer that creates surface tension.
High surface tension tends to collapse alveoli, especially during expiration.
Surfactant reduces this surface tension.
Step 3: Functional Importance.
By reducing surface tension, surfactant stabilizes alveoli of different sizes.
It prevents atelectasis (alveolar collapse).
This ensures proper lung expansion and efficient breathing.
Step 4: Evaluation of Other Options.
Gas exchange is primarily performed by the alveolar-capillary membrane.
Surfactant decreases, not increases, surface tension.
Mucociliary clearance occurs in the respiratory tract, not alveoli.
Step 5: Conclusion.
Therefore, the primary function of pulmonary surfactant is to prevent alveolar collapse.