Pulmonary surfactant lowers alveolar surface tension primarily because of which constituent synthesized by type II pneumocytes?
- A Phosphatidylinositol
- B Dipalmitoylphosphatidylcholine ✓
- C Sphingomyelin
- D Cholesterol esters
Correct answer: B. Dipalmitoylphosphatidylcholine
Explanation
Dipalmitoylphosphatidylcholine, also called lecithin, is the principal phospholipid responsible for reducing alveolar surface tension; its saturated palmitic chains pack tightly at the air liquid interface. The lecithin to sphingomyelin ratio in amniotic fluid rises above 2 after about 34 weeks, reflecting lung maturity. Phosphatidylinositol rises slightly later and adds stability, but it is not the main surface active molecule. Sphingomyelin serves as the comparison marker, not the active agent.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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