The portion of the respiratory system where air does not participate in gas exchange, including the trachea and bronchi?

• A. Alveolar Space
• B. Functional Residual Capacity
• C. Dead Space in Lungs
• D. Tidal Volume

Answer: (C)

The main idea is distinguishing where air actually exchanges gases with the blood. The trachea and bronchi are part of the conducting airways that move air to the lungs but don’t participate in gas exchange themselves. The air there is just passing through, conditioning the air (warming, humidifying) before it reaches the alveoli. That portion is called anatomical dead space. Gas exchange happens in the alveolar spaces, so those areas are not dead space. Functional residual capacity is a lung volume left after normal expiration, and tidal volume is the amount moved in and out with a breath; neither describes a region where gas exchange is completely absent. So the correct concept is dead space in the lungs.