Final answer:
The tracheobronchial tree is lined by pseudostratified ciliated columnar epithelium with goblet cells and cilia, which aid in trapping and removing debris. The cilia disappear as the airways narrow, and the epithelium becomes simple squamous in the alveoli.
Step-by-step explanation:
The tracheobronchial tree from the trachea to the respiratory bronchioles is lined by pseudostratified ciliated columnar epithelium. This epithelium contains goblet cells which produce mucus that traps debris and pathogens. The cilia on the apical surface of these cells help to move mucus and trapped particles out of the respiratory tract, ensuring protection from invasive microorganisms and other harmful materials inhaled into the body.
The cilia are present from the trachea down through the bronchi and bronchioles but disappear as the bronchioles narrow and approach the alveoli. At this point, the epithelium gradually changes, and by the time the airway reaches the alveoli, it becomes a simple squamous epithelium. Therefore, the cilia are absent in the alveolar ducts and the alveoli themselves, where gas exchange occurs.