What is the importance of maintaining negative pressure in the pleural cavity?

• A. To prevent inhalation of pollutants
• B. To assist in lung expansion during inhalation
• C. To enable gas exchange
• D. To regulate air temperature

Answer: (B)

Maintaining negative pressure in the pleural cavity plays a crucial role in assisting lung expansion during inhalation. The pleural cavity, located between the visceral and parietal pleura, contains a small amount of pleural fluid and is essential for facilitating respiratory mechanics.

When the diaphragm contracts and the intercostal muscles expand the thoracic cavity during inhalation, the volume of the pleural cavity increases. The negative pressure created within this cavity is what allows the lungs to expand. This negative pressure relative to the atmospheric pressure ensures that the lungs inflate properly, preventing them from collapsing and promoting effective ventilation.

If the pleural pressure were to become equal to or exceed atmospheric pressure, the lungs would be unable to expand, leading to respiratory complications. Therefore, the negative pressure in the pleural cavity is vital for the mechanics of breathing and effective gas exchange in the alveoli.