The bronchiolar epithelium in cigarette smokers. Observations with the scanning electron microscope.

Observations with the scanning electron microscope were made on the bronchiolar epithelium of 25 lungs removed at surgery. In all but 3 cases, the lungs were removed for a malignant tumor. Abundant ciliated cells were present in all lung specimens. In lungs obtained from nonsmokers, numerous Clara cells were present in the small bronchioles, whereas goblet cells were seen, and in most cases, the Clara cells were infrequent or absent. The evidence for the secretory nature of the Clara cells is discussed as is the possible effect on lung function of alteration in the type of secretory cell in the bronchioles.