Human Lung Structure, Function, and Clinical Links

Lung role in respiratory gas exchange

The lungs are the primary organs responsible for respiratory gas exchange. Air travels from the trachea into bronchi and bronchioles, eventually reaching microscopic alveoli, where oxygen diffuses from the air into the bloodstream and carbon dioxide diffuses from the blood into the air to be exhaled. This gas exchange occurs in the lung’s respiratory zone, beginning when conducting airways branch into respiratory bronchioles and form the terminal respiratory units (e.g., acini) containing alveoli. Gas exchange depends on the lung’s specialized structure and blood supply. Alveolar walls are extremely thin to allow rapid diffusion, and the alveoli are closely associated with capillary networks. The lungs also maintain airflow and diffusion efficiency through their elastic connective tissue (supporting lung compliance and recoil) and through respiratory epithelium that supports airway patency and clearance. In addition, the lungs have distinct circulations: pulmonary circulation delivers deoxygenated blood for oxygenation, while bronchial circulation supplies oxygenated blood to lung tissue itself.

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Breathing mechanisms across animal groups

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