Contraction of the diaphragm and external intercostals does what to the thoracic cavity and the pressure inside it?

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Multiple Choice

Contraction of the diaphragm and external intercostals does what to the thoracic cavity and the pressure inside it?

When the diaphragm contracts, it moves downward, and the external intercostals lift the rib cage, both actions enlarging the thoracic cavity. As the volume inside the chest increases, the pressure inside the thoracic cavity falls (the intrapulmonary pressure becomes lower than atmospheric pressure). This drop in pressure creates a gradient that pulls air into the lungs until pressures equalize. So the correct idea is that the thoracic cavity becomes larger and the pressure inside decreases. The other options don’t fit this pattern: shrinking volume would raise pressure, no change would not allow air movement, and saying pressure rises while volume increases contradicts the inverse relationship between volume and pressure described by Boyle’s law.

When the diaphragm contracts, it moves downward, and the external intercostals lift the rib cage, both actions enlarging the thoracic cavity. As the volume inside the chest increases, the pressure inside the thoracic cavity falls (the intrapulmonary pressure becomes lower than atmospheric pressure). This drop in pressure creates a gradient that pulls air into the lungs until pressures equalize.

So the correct idea is that the thoracic cavity becomes larger and the pressure inside decreases. The other options don’t fit this pattern: shrinking volume would raise pressure, no change would not allow air movement, and saying pressure rises while volume increases contradicts the inverse relationship between volume and pressure described by Boyle’s law.

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