Amount of surfactant in the developing lung increases between the 26th and 32nd weeks of gestation. This increase is related to which of the following developmental events?

Surfactant is synthesized by Type II pneumocytes that line the alveolar sacs. They begin to differentiate after the 26th week of Gestation. These cells can be recognized on electron microscopy by the presence of lamellar bodies. Surfactant production increases greatly after 35 weeks' gestation. Other structures in the lung do not synthesize the phosphatidylcholine and phosphatidylglycerol compounds that are impoant in reducing alveolar surface tension.