During inspiration, the diaphragm contracts and moves downwards, increasing the volume of the thoracic cavity. This results in a decrease in intra-alveolar pressure, causing air to flow into the lungs. The internal intercostal muscles are not involved in normal inspiration, but rather in forced expiration.

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During Inspiration

Question 6

Multiple Choice

During inspiration

A) Intra-alveolar pressure falls below atmospheric pressure.
B) The diaphragm contracts.
C) The internal intercostal muscles contract.
D) Intra-alveolar pressure falls below atmospheric pressure and the diaphragm contracts.
E) All of these.

Correct Answer: