Overview The respiratory system maintains gas homeostasis by enabling oxygen uptake and carbon dioxide removal. Through coordinated mechanical ventilation and diffusion across the alveolar membrane, the lungs support cellular metabolism and acid–base balance. Respiratory physiology integrates airflow dynamics, gas exchange, and neural control to sustain effective ventilation. Key Topics This section includes core principles of pulmonary ventilation, airway resistance, and the mechanics of breathing. It also examines gas exchange at the alveolar–capillary interface, ventilation–perfusion relationships, and the regulation of respiration. Together, these topics explain how airflow, perfusion, and neural control mechanisms interact to optimise oxygen delivery. Clinical Relevance and Learning Focus Disturbances in ventilation, diffusion, or respiratory control can impair oxygenation and acid–base stability. Understanding respiratory physiology supports interpretation of blood gases, lung function testing, and patterns of respiratory compromise. This section promotes systems-level understanding, linking mechanics, gas transport, and neural regulation to clinical presentation and physiological adaptation.