Which lung volume helps keep the lungs open after exhalation?

• A. Tidal Volume
• B. Dead Space
• C. Inspiratory Reserve Volume
• D. Residual Volume

Answer: (D)

The main idea is that a portion of air stays in the lungs after exhalation to keep the lungs from collapsing and to maintain some inflation between breaths. This remaining air is residual volume, the amount left after a maximal exhale. It ensures the alveoli stay open and ready for the next breath, supporting continuous gas exchange.

Tidal volume is the amount moved with a normal breath, not about what remains after exhalation. Dead space refers to air in the conducting airways that doesn’t participate in gas exchange. Inspiratory reserve volume is the extra air you can inhale beyond a normal breath. Residual volume specifically describes the air that keeps the lungs inflated after exhalation.