Question

What are the changes in thoracic volume and sequence of events during inspiration and expiration? Explain.

Note: Please write or type all answers in a way that is understandable and legible. hank you for taking the time to answer my question!

Answer 1

Answer :

Inspiration :

Intake of atmospheric air into the lungs is called inspiration. It is an active process, as it takes place by the contraction of muscles of the diaphragm and the external inter - costal muscles, which extand in between the ribs. The contraction of the diaphragm ( phrenic muscles) increase the volume of the thoracic chamber in the antero- posterior axis. The contraction of external inter- costal muscles lifts up the ribs and sternum causing an increase in the volume of the thoracic chamber in the dorso- ventral axis. The overall increase in the thoracic volume causes a similar increase in the pulmonary volume. An increase in the pulmonary volume decreases the intra- pulmonary pressure to less than that of the atmosphere, which forces the air from the outside to move into the lungs, I. e inspiration.

Expiration :

Release of alveolar air to the exterior is called expiration. It is a passive process. Relaxation of the diaphragm and the external inter- costal muscles returns the diaphragm and sternum to their normal position, and reduce the thoracic volume and thereby the pulmonary volume. This leads to an increase in the intra- pulmonary pressure to slightly above that of the atmospheric pressure, causing the expulsion of air from the lungs, i. e. expiration.