Phases of Lung Maturation

The document summarizes the development and maturation of the lungs from early gestation through childhood in four stages: 1) Pseudoglandular stage (6-16 weeks): Major lung elements form except those for gas exchange. No alveoli or respiratory bronchioles. 2) Canalicular stage (16-26 weeks): Bronchioles divide and lung tissue becomes highly vascular. Respiratory bronchioles form but no alveoli. 3) Terminal sac stage (26 weeks to birth): Thin-walled sacs form and come into close contact with capillaries to enable gas exchange. Lungs are capable of respiration. 4) Alveolar stage (late