What occurs to the intrapleural pressure during normal expiration?

During normal expiration, the intrapleural pressure returns to the value at rest. This process occurs as the muscles involved in breathing relax after contraction during inhalation. When the diaphragm and intercostal muscles relax, the thoracic cavity volume decreases, which leads to an increase in intrapulmonary pressure, causing air to flow out of the lungs. As the lungs deflate, the pleural pressure also rises, but it returns to its resting level rather than dropping further or remaining constant. This change reflects the dynamic nature of intrapleural pressure in relation to lung volume and the respiratory cycle.

Understanding this mechanism is crucial, as it illustrates how pressure changes associated with breathing contribute to the ventilation process and the overall function of the respiratory system.