During which fetal lung development stage does surfactant production begin?

Surfactant production begins during the canalicular stage of fetal lung development. This stage occurs roughly between 16 to 24 weeks of gestation. During this period, the airways continue to branch and the epithelial cells begin to differentiate into type II alveolar cells, which are responsible for producing surfactant. This critical fluid helps reduce surface tension in the alveoli, preventing their collapse and allowing for proper lung expansion and gas exchange at birth.

In contrast, the embryonic stage encompasses the initial development of the lung structures but does not involve surfactant production. Similarly, while the pseudoglandular stage features the branching and formation of the conducting airways, surfactant production has not yet commenced. The saccular stage follows the canalicular stage and is characterized by the development of sac-like structures that will ultimately mature into alveoli, where surfactant is present but production began earlier during the canalicular stage. Thus, the timing and specific processes of surfactant production are most accurately linked to the canalicular stage.