The surfactant layer increases alveolar surface tension to stabilize the alveoli during both inhalation and exhalation, preventing overexpansion of the lungs and ensuring steady oxygen diffusion.

Surfactant is secreted continuously from the fetal trachea throughout gestation to lubricate airways and enhance mucus clearance, facilitating respiratory function immediately after birth.

Surfactant production peaks at 20 weeks gestation and remains stable throughout pregnancy: therefore, preterm infants born after this point typically do not experience respiratory complications related to lung immaturity.

Pulmonary surfactant production begins between 24 to 28 weeks gestation, primarily from type II alveolar cells: its primary role is to lower alveolar surface tension, preventing atelectasis and promoting lung compliance, which is critical for effective gas exchange after birth.