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The respiratory bronchioles are lined with simple cuboidal epithelium, which plays a crucial role in the respiratory system. This type of epithelium is specifically adapted for gas exchange while still providing some structural support. Simple cuboidal epithelium consists of a single layer of cube-shaped cells that facilitates the exchange of gases due to its relatively thin nature, allowing for effective diffusion.

As respiratory bronchioles are the transitional structures between the conducting airways and the gas-exchanging alveoli, their cuboidal lining also includes Clara cells (or club cells), which are non-ciliated and contribute to the secretion of surfactant and play a protective role in the airway. The presence of this type of epithelium in respiratory bronchioles reflects the shift from the more complex epithelium found in larger airways, like ciliated columnar epithelium, to a simpler structure that is more suited for the functions of respiration at this level of the airway.

In contrast, the other types of epithelium listed do not accurately represent the cellular composition of respiratory bronchioles. Simple squamous epithelium, while present in the alveoli for efficient gas exchange, is not found in bronchi