The diaphragm contracts and flattens during inhalation. What effect does this have on intrathoracic pressure?

The diaphragm contracts and flattens during

Multiple choice — select the best answer

AIt decreases, drawing air into the lungs
BIt increases, pushing air out of the lungs
CIt remains unchanged
DIt causes the alveoli to collapse

✓ Correct answer: A. It decreases, drawing air into the lungs When the diaphragm contracts, thoracic volume increases, causing intrathoracic pressure to drop below atmospheric pressure; air flows down this gradient into the lungs. Exhalation is largely passive as the diaphragm relaxes.

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Topic: Body Systems

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The diaphragm contracts and flattens during inhalation. What effect does this have on intrathoracic pressure?

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