During exhalation, what happens to the intrathoracic pressure?

During exhalation, the intrathoracic pressure increases. This process occurs because the diaphragm and intercostal muscles relax, causing the thoracic cavity to decrease in volume. As the volume of the thoracic cavity decreases, the pressure within it rises relative to the atmospheric pressure outside the body.

This increased intrathoracic pressure facilitates the expulsion of air from the lungs, pushing it out into the atmosphere. The mechanics of breathing are fundamentally tied to changes in pressure, where the movement of air in and out of the lungs is driven by these pressure differentials. Therefore, recognizing that intrathoracic pressure increases during exhalation is crucial for understanding respiratory physiology.