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Human lungs - class-XI

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Which of the following changes occur in diaphragm and intercostal muscles when expiration of air takes place? 

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A
Internal intercostal muscles contract and diaphragm relax
💡 Explanation:
  • When the internal intercostal muscles contract and diaphragm relax, the ribs move .downward and inward and the diaphragm becomes convex {dome shaped), 
  • thus decreasing the volume of the thoracic cavity and increasing the pressure inside as compared to the atmospheric pressure outside. This will cause the air to move out (expiration).
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