At What Gestational Age Do Primitive Respiratory Bronchioles Appear

Question

At what gestational age do primitive respiratory bronchioles appear?
A) 12-16 weeks
B) 25-28 weeks
C) 17-26 weeks
D) 8-12 weeks

Accepted Answer

Primitive respiratory bronchioles appear during the pseudoglandular stage of lung development, which occurs approximately between 5 to 17 weeks of gestation. However, the specific timeframe for the appearance of primitive respiratory bronchioles is generally placed within the range of 17-26 weeks, marking the transition into the canalicular stage, where the lung structures become more refined and capable of supporting gas exchange if birth occurs prematurely.