What are the alveoli and distal gas-exchange regions collectively known as?

The alveoli and distal gas-exchange regions are collectively known as the respiratory division. This term encompasses the areas where gas exchange occurs, primarily in the alveoli, which are tiny air sacs in the lungs. The respiratory division is crucial for the functioning of the respiratory system as it includes unique structures directly involved in the exchange of oxygen and carbon dioxide between the air and blood.

The alveoli are specifically designed to maximize surface area for gas exchange and are lined with a thin membrane that facilitates this process. This region is distinct from other parts of the respiratory system, such as the conducting pathways, which include the trachea and bronchi that serve primarily to transport air to the lungs but do not take part in gas exchange. The upper respiratory tract, which includes structures like the nasal cavity and pharynx, is also primarily involved in filtering and humidifying the air before it reaches the lungs. Conversely, the lower respiratory tract includes structures beyond the conducting pathways but does not specifically denote the alveolar regions where gas exchange occurs.

Hence, identifying the alveoli and distal gas-exchange regions as the respiratory division is accurate as it directly relates to their function and location in the lung anatomy.