surfactant

This term describes substances that modify the physical interface between different phases of matter. In industrial and domestic settings, it is most commonly associated with soaps and detergents that allow water to penetrate oily surfaces by reducing surface tension. In a biological context, it refers specifically to the critical lipid-protein complex in the lungs. Without this substance, the high surface tension of the fluid lining the alveoli would cause the lungs to collapse during expiration, making it a vital component for neonatal survival.