During exhalation, where is the pressure increased in the body?

During exhalation, the pressure in the thoracic cavity increases as the diaphragm and intercostal muscles relax. This reduction in the volume of the thoracic cavity leads to an increase in pressure relative to the atmospheric pressure. As a result, air is expelled from the lungs. The dynamics of breathing involve the thoracic cavity acting as a pressure reservoir, which is essential for effective respiration.

The abdominal cavity, while it does experience changes in pressure during respiration, primarily serves as a support structure for the diaphragm, and the pressure increase during exhalation is not as prominent or significant as that in the thoracic cavity. Similarly, the cervical and pelvic cavities do not play direct roles in the changes in intrathoracic pressure associated with normal respiration; hence, they are not the focus during the exhalation process. Understanding this anatomy and physiology highlights the thoracic cavity's crucial role in breathing mechanics.