What happens to the lungs when the diaphragm relaxes?

• A. The lungs remain unchanged and air flow stops.
• B. The lungs expand and air is drawn in.
• C. The lungs contract and air is expelled.
• D. The lungs fill with fluid and breathing becomes difficult.

Answer: (C)

Verified step by step guidance

1. Understand the role of the diaphragm in breathing: The diaphragm is a dome-shaped muscle located at the base of the lungs. It plays a crucial role in the process of inhalation and exhalation.
2. Recognize the process of inhalation: When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity and decreasing the pressure inside the lungs, allowing air to flow in.
3. Identify the process of exhalation: When the diaphragm relaxes, it moves upward into its dome shape, decreasing the volume of the thoracic cavity and increasing the pressure inside the lungs.
4. Relate diaphragm relaxation to lung function: As the diaphragm relaxes and the thoracic cavity volume decreases, the pressure inside the lungs becomes greater than the atmospheric pressure, causing air to be expelled from the lungs.
5. Conclude the effect of diaphragm relaxation: Therefore, when the diaphragm relaxes, the lungs contract and air is expelled, which aligns with the correct answer provided.