The pleural space lies between which two membranes?

• A. Visceral and parietal pleura
• B. Peritoneum and mesentery
• C. Endocardium and epicardium
• D. Inner and outer membranes of the chest wall

Answer: (A)

The pleural space is the thin potential space between the two pleural membranes: the visceral pleura that covers the lungs and the parietal pleura that lines the inside of the chest wall and diaphragm. This arrangement creates a virtual gap where a small amount of lubricating fluid sits, and the negative pressure in this space helps keep the lungs expanded against the chest wall. The other options refer to different organs or vague membranes and do not define the pleural cavity. Understanding this separation is key when considering chest tube function, since drainage of air or fluid from this space allows the lung to re-expand.