When the diaphragm contracts
A) The volume of the thoracic cavity increases.
B) Lung volume increases as the lungs are forced to expand.
C) The intra-alveolar pressure increases.
D) The volume of the thoracic cavity increases and lung volume increases as the lungs are forced to expand.
E) All of these.

Question

Quizplus · Accepted Answer

When the diaphragm contracts, the volume of the thoracic cavity increases, which leads to lung volume increasing as the lungs are forced to expand. This expansion decreases the intra-alveolar pressure, allowing air to flow into the lungs. Therefore, both D options are correct.

When the Diaphragm Contracts