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Trachea and primary bronchus
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x

Epithelium
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x

Lamina propria
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x

- Elastic lamina
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x

- Elastic fibers (xs)
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x

- Mixed glands
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x

- Ducts
Another image of the trachea or primary bronchus demonstrates the layers adjacent to the lumen. The longitudinally oriented elastic fibers in the elastic lamina are seen cut in cross section. No smooth muscle layer is visible in this image. 400x