At what gestational week does alveolar formation begin?

Alveolar formation, which is part of the development of the lungs in the fetus, begins around 24 to 28 weeks of gestation. The period of alveolar development is critical as it signifies the maturation of the lungs, preparing them for function at birth.

At approximately 28 weeks of gestation, there is a significant increase in the number of alveoli being formed, making this a key milestone in lung development. Hence, while alveolar formation technically starts earlier, the correct answer to reflect significant lung maturation and development would be 28 weeks, specifically noting that the majority of the alveolar development occurs between 28 and 36 weeks.

After this period, particularly approaching 36 weeks, the lungs are generally more developed with increased alveolar surface area, readying the fetus for the transition to breathing air outside the womb.