pulmonary surfactant

https://doi.org/10.1351/goldbook.11270

Surface-active layer of phospholipids and proteins coating the pulmonary alveoli that increases lung compliance, facilitates lung expansion, and stabilizes alveolar volume.

Note: Lack of pulmonary surfactant is more common following premature birth and is a cause of infant respiratory distress syndrome.
Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 810 [Terms] [Paper]