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Q.
Which of the following changes occur in diaphragm and intercostal muscles when expiration of air takes place?
Breathing and Exchange of Gases
Solution:
When the internal intercostal muscles contract and diaphragm relax, the ribs move downward and inward and diaphragm becomes convex (dome shaped), thus decreasing the volume of thoracic cavity and increasing the pressure inside as compared to the atmospheric pressure outside. This will cause the air to move out (expiration).