Table 1.

Summary of Major Differences between Human and Mouse Lungs

	Human	Mouse
Size	Trachea, 1.5–2 cm; >20 airway generations	Trachea, 1.5 mm; 13–17 airway generations
Mechanical forces	Mostly upright	Mostly prone
Cartilage	Trachea and intrapulmonary bronchi for several bronchial generations	Trachea and only extrapulmonary bronchi
Submucosal glands	Throughout cartilaginous airways	First three cartilage rings of trachea
Epithelial composition	Goblet cells, low number of club cells restricted to small airways	Few goblet cells (unless injured), club cells line all conducting airways
Basal cells	Trachea and extrapulmonary and intrapulmonary bronchi, extending to terminal bronchioles	Trachea and extrapulmonary bronchi only
Neuroendocrine cells	Cells found throughout airway epithelium; clusters found only within intrapulmonary airways	Mostly clustered
Respiratory bronchiole	Present	Absent
Proximal–distal patterning	SOX2 and SOX9 co-expression in tip progenitors in pseudoglandular stage	Sox2 expression absent in Sox9+ tip progenitors in pseudoglandular and canalicular stages
Developmental timing	Alveologenesis initiates before birth	Alveologenesis initiates after birth

Definition of abbreviation: SOX = SRY-box transcription factors.