PHYSIOLOGY
PULMONARY PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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An increase in the volume of the thoracic cavity
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Increase in alveolar pressure
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A decrease in lung volume
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A decrease in the volume of the thoracic cavity
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Detailed explanation-1: -Upon inhalation, the diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls air into the lungs. Upon exhalation, the diaphragm relaxes and returns to its domelike shape, and air is forced out of the lungs.
Detailed explanation-2: -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.
Detailed explanation-3: -External intercostal muscles contract pulling the ribs upwards and outwards. The diaphragm which is a flat sheet of muscle extending across the bottom of the rib cage contracts and flattens out. These two actions enlarge the thoracic cavity surrounded the lungs, thereby increasing the volume of the lungs.