@viscera3d: The foundation of the respiratory system is the bronchial tree, terminating in the alveolar apparatus. Passive gas diffusion occurs across the ultra-thin alveolo-capillary membrane driven by pressure gradients: O₂ enters the systemic circulation, while CO₂ is excreted into the alveoli. A total respiratory surface area of ~100 m² ensures continuous tissue oxygenation. #pulmonology #anatomy #physiology #gasexchange #lungs