During inhalation, what changes occur in the diaphragm?

• A. The diaphragm relaxes and moves upward.
• B. The diaphragm contracts and moves downward.
• C. The diaphragm stops moving.
• D. The diaphragm expands outward.

Answer: (B)

The main idea is how the diaphragm drives inhalation. When you inhale, the diaphragm contracts. This contraction pulls the diaphragm downward, flattening it from its dome shape and increasing the vertical volume of the thoracic cavity. As the chest cavity expands, the pressure inside drops slightly below atmospheric pressure, drawing air into the lungs.

If the diaphragm relaxed and moved upward, the chest would become smaller and air would be pushed out rather than drawn in. If it stopped moving, there would be no change in thoracic volume to create the pressure difference needed for inhalation. The diaphragm doesn’t expand outward; it moves downward when it contracts, which is the key action that initiates inhalation.