Excerpt - The lower respiratory system (shown in Figure 25.2) plays a crucial role in respiration, allowing the exchange of oxygen and carbon dioxide between the body and the external environment. The lower respiratory system includes the trachea, the lungs, and within the lungs, the bronchi, bronchioles, and alveoli. See Introduction to the Respiratory System for more information on the lower and upper respiratory systems. Various respiratory diseases and disorders can significantly affect the functioning of the lower respiratory system, leading to respiratory distress, impaired lung function, and reduced quality of life. Lower respiratory drugs are a class of medications designed to alleviate symptoms, manage chronic conditions, and improve overall respiratory function.