What happens to intrapleural pressure during inspiration?

• A. It decreases
• B. It increases
• C. It remains the same
• D. It fluctuates

Answer: (A)

During inspiration, intrapleural pressure decreases. This occurs because as the diaphragm and intercostal muscles contract, the thoracic cavity expands. This expansion increases the volume of the thoracic cavity, which in turn reduces the pressure within the pleural space (the area between the lung surface and the chest wall).

The decrease in intrapleural pressure is crucial as it creates a pressure gradient that allows air to flow into the lungs. When intrapulmonary pressure (the pressure within the lungs) becomes lower than atmospheric pressure due to the expansion of the thoracic cavity, air rushes into the lungs, facilitating the process of breathing. Thus, the decrease in intrapleural pressure is an essential part of the mechanics of ventilation, ensuring effective gas exchange.