Trachea

Bronchioles

Clara cells

nonciliated; secrete a serous solution similar to surfactant

detoxify airborne toxins

serve as stem cell for the ciliated cells and for themselves

most abundant in terminal bronchioles (80% of epithelial lining)

also involve in chloride ion transport into the lumens of the terminal bronchioles

Alveolus

Type I pneumocyte

squamous; only 40% of the alveolar lining cells, but cover 90 -95% of the surface

Type II pneumocyte

60% of the alveolar lining cells, but cover only 5-10% of the surface

serve as stem cells