Fig. 1

Terms associated with prenatal and postnatal development of the alveolar parenchyma organized by age_range. Development of the alveolar parenchyma is organized into 4 developmental stages, or age_range(s), each with unique terminology for pre- and post-natal alveolar structures. These age_range(s) are E16.6-E17.5 (canalicular stage); E18.5-E19.5/birth (saccular stage, prenatal period); P0-P3 (saccular stage, postnatal period); P4-P36 (alveolar stage). Terms for the alveolar parenchyma (enclosed in boxes) differ with developmental stage as these structures evolve over time