What happens to intrapleural pressure during inspiration?

• A. It becomes more positive
• B. It becomes less negative
• C. It remains constant
• D. It becomes more negative

Answer: (D)

During inspiration, the diaphragm and intercostal muscles contract, leading to an increase in the volume of the thoracic cavity. As the volume increases, the intrapleural space, which is located between the lungs and the chest wall, experiences an increase in volume as well. According to the principles of physiology, when the volume of a confined space increases, the pressure within that space decreases.

Therefore, the intrapleural pressure becomes more negative during inspiration. This negative pressure is crucial because it helps keep the lungs inflated; the greater negative pressure relative to the atmospheric pressure allows air to flow into the lungs as they expand. This process is essential for ventilation and gas exchange in the respiratory system.

This phenomenon highlights the dynamic relationship between lung mechanics and intrapleural pressure during the breathing process. Understanding this response is fundamental in pathophysiology, especially in conditions where intrapleural pressure dynamics are altered, such as in pneumothorax or restrictive lung diseases.