Clinical Sonography III Practice Exam

During inspiration, which of the following occurs?

Diaphragm descends Diaphragm ascends Intra-abdominal pressure decreases Intra-thoracic pressure increases

Correct Answer:

Diaphragm descends

Explanation:

During inspiration the diaphragm contracts and moves downward, enlarging the thoracic cavity. This downward movement increases thoracic volume and lowers intrathoracic pressure below atmospheric level, creating a negative pressure gradient that pulls air into the lungs. The diaphragm does not ascend during inspiration; and intrathoracic pressure does not rise—inspiration actually lowers it. While the abdominal contents are pushed downward, causing a slight rise in intra-abdominal pressure, the key observable effect related to air flow is the diaphragmatic descent and the resulting drop in intrathoracic pressure.

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