Epithelial Lining of Air Passages
The structure of the respiratory tubes is well designed to transport air into the alveoli in all parts of the lung and the structure of the epithelial lining is well suited to its function as an air filter:
This epithelium is called pseudostratified ciliated columnar epithelium and is found lining the trachea, bronchi and larger bronchioles. The mucus is secreted by specialised cells called goblet cells. The layer of mucus is kept moving by the action of finger-like projections called cilia.