The contraction of the diaphragm and the external intercostal muscles begins inspiration. Explain exactly what happens, in terms of volume and pressure changes in the lungs, when these muscles contract
What will be an ideal response
With contraction of the diaphragm, the height of the thoracic cavity increases. Contraction of the external intercostal muscles expands the diameter of the thorax. With an increase in volume of the thorax, the intrapulmonary volume increases, causing a drop in pressure relative to atmospheric pressure. Air rushes into the lungs along this pressure gradient until intrapulmonary and atmospheric pressures are equal.
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