are fluid filled spaces situated between the visceral and parietal pleurae of the lungs.

• A. Pericardial cavity
• B. Pleural cavity
• C. Mediastinum cavity
• D. Abdominal cavity

Answer: (B)

The space between the lung’s visceral pleura and the chest wall’s parietal pleura is the pleural cavity. This fluid-filled potential space contains a small amount of pleural fluid that lubricates the surfaces so the lungs can slide smoothly against the chest wall as you breathe. The visceral pleura covers the lungs, while the parietal pleura lines the thoracic cavity, including the mediastinum and diaphragm. The other options don’t describe this space: the pericardial cavity surrounds the heart, the mediastinum is a central compartment that contains structures like the heart and great vessels, and the abdominal cavity houses abdominal organs.