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What is the role of pulmonary surfactant in the lungs?
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human respiratory system
The lungs serve as the gas-exchanging organ for the process of respiration.
Pulmonary surfactant is a complex mixture of lipid and protein molecules secreted by type II pneumocytes in the lungs. Its primary physiological roles include:12
- Reducing Surface Tension: Surfactant lines the alveolar surface, significantly lowering the surface tension that exists at the gas-liquid interface of the alveoli.324
- Preventing Alveolar Collapse: By reducing surface tension, surfactant prevents the tiny air sacs (alveoli) from collapsing.24
- Stabilizing Alveoli: Because alveoli vary in size, uniform surface tension would otherwise cause smaller alveoli to collapse into larger ones. Surfactant changes surface tension in a nonlinear way, stabilizing alveoli of different sizes and preventing this unstable condition.3
By maintaining these open air spaces, surfactant ensures that the lungs can function efficiently for gas exchange. If surfactant accumulates excessively, as seen in conditions like pulmonary alveolar proteinosis, it can hinder gas exchange and lead to respiratory distress.14