what is surfactant in the lungs

Surfactant is a mixture of fat and proteins that is produced in the lungs, specifically by type II alveolar epithelial cells. It lines the alveoli, which are the air sacs in the lungs where oxygen enters the body, and lowers surface tension, thereby preventing atelectasis during breathing. Surfactant is essential for life, and its specific function is to reduce surface tension at the pulmonary air-liquid interface. Without normal surfactant, the tissue surrounding the air sacs in the lungs sticks together after exhalation, causing the alveoli to collapse. As a result, filling the lungs with air on each breath becomes very difficult, and the delivery of oxygen to the body is impaired. Surfactant replacement therapy is used to treat premature infants who may be born before their lungs make enough surfactant. Using surfactant has been shown to reduce pneumothorax (collapsed lung) and increase survival rates significantly.