Squamous metaplasia of the opening of bronchial glands.

The major bronchi of swine, a dog and rabbits were examined with a scanning electron microscope and the fine structure of the openings of bronchial glands were studied three-dimensionally. The smallest areas of squamous metaplasia involved the duct openings. By examining serial sections with the light and transmission electron microscopes these early lesions were found localized at the opening of the bronchial gland duct. Cells intermediate to goblet and squamous cells were present in these lesions. Squamous metaplasia starting at this particular location is probably common and metaplasia can be an intracellular process.