What is the capacity of the pleural space?

• A. 500 mL
• B. 3000 mL
• C. 1000 mL
• D. 2500 mL

Answer: (B)

The pleural space is a potential cavity between the lungs and chest wall that normally contains only a tiny amount of lubricating fluid, but it can hold a substantial volume when fluid accumulates. Its capacity is about 3,000 mL (roughly 3 liters), which is the amount the space can accommodate before the lungs’ expansion is severely limited. That’s why the 3,000 mL estimate is the best match: smaller volumes would not reflect how much the space can hold in conditions like large pleural effusions, while 3,000 mL aligns with clinical teaching about the space’s maximal capacity.