Question

During inhalation, how does intrapulmonary pressure change relative to atmospheric pressure? How does the body accomplish this change in pressure? During exhalation, how does intrapulmonary pressure change relative to atmospheric pressure? How does the body accomplish this change in pressure?

Answer 1

Answer) During inhalation, intrapulmonary pressure decreases i.e 759 mmHg relative to atmospheric pressure i.e 760 mmHg.

The body accomplish this change in the pressure by changing in thoracic cavity volume.

During inhalation, contraction of external intercostal muscles and muscles of diaphragm takes place,which causes increase in thoracic cavity volume.

The increase in thoracic volume causes increase in pulmonary volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than of the atmospheric pressure, which forces the air from outside to move into the lungs i.e inspiration.

During exhalation, intrapulmonary pressure increases i.e 761 mmHg relative to atmospheric pressure i.e 760 mmHg.

This occurs also due to change in thoracic cavity volume.

During exhalation, relaxation of external intercostal muscles and muscles of diaphragm occurs. This causes decrease in thoracic cavity volume and thereby decrease in pulmonary volume.

This decrease in pulmonary volumes leads to increase in the intrapulmonary pressure to slightly above to that of atmospheric pressure, causing of expulsion of air from the lungs i.e expiration.