What is the primary cause of collapse in small alveoli in premature infants?

The primary cause of collapse in small alveoli in premature infants is inadequate surfactant production. Surfactant is a substance composed primarily of lipids and proteins that is secreted by the epithelial cells of the alveoli. Its primary role is to reduce surface tension within the alveoli, which helps keep them open and prevents their collapse during exhalation.

In premature infants, the lungs may not be fully developed, leading to insufficient production of surfactant. This condition is commonly referred to as neonatal respiratory distress syndrome (NRDS). Without enough surfactant, the surface tension in the smaller alveoli becomes too high for them to remain open, resulting in their collapse (atelectasis) and impaired gas exchange. Thus, the lack of adequate surfactant production is a critical factor in the respiratory issues faced by premature infants, making it the correct answer in this context.

The other factors mentioned, such as lack of oxygen and structural immaturity, can certainly contribute to respiratory problems, but they are not the primary cause of alveolar collapse. Pulmonary edema can complicate the situation, but it is not the core issue relating to the lack of surfactant.