EMBRYOLOGY
RESPIRATORY SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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the volume of the thoracic cavity increases and the pressure decreases, causing air to rush into the lungs.
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the volume of the thoracic cavity decreases and the pressure increases causing air to rush out of the lungs.
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Either A or B
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None of the above
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Detailed explanation-1: -When the lungs inhale, the diaphragm contracts and pulls downward. At the same time, the muscles between the ribs contract and pull upward. This increases the size of the thoracic cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs.
Detailed explanation-2: -As the diaphragm contracts (moves downward), the volume of the thoracic cavity increases and the intra-alveolar pressure decreases from an atmospheric pressure of 760mmHg to 756mmHg. A pressure gradient is established and air enters the lungs. The external intercostal muscles also assist inspiration.
Detailed explanation-3: -Lung volume expands because the diaphragm contracts and the intercostals muscles contract, thus expanding the thoracic cavity. This increase in the volume of the thoracic cavity lowers pressure compared to the atmosphere, so air rushes into the lungs, thus increasing its volume.