Bronchiolar epithelium 
Epithelial lining fluid 
Cilated cell Clara cell 
Basement 
membrane 
Figure 1.9.2-B. Major cell types of the walls of the bronchioles. The 
epithelium is columnar and rests on a basement membrane. There are two 
major cell types; ciliated cells and Clara cells. There are no submucosal 
glands. The airway epithelial lining fluid is thinner than observed in the 
larger airways and a distinct mucus layer is not apparent. 
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