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Respiration and Circulation — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYRespiration and Circulation3 Marks
Question
Give reasons : Expiration is called a passive process.
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Answer

  1. During expiration, intercostal muscles relax. This results in pulling the ribs inwards.
  2. Diaphragm also relaxes and returns to its normal dome shape.
  3. The collective contraction of ribs and diaphragm results in the reduction of
    thoracic cavity and hence automatically air is pushed out of the lungs.
  4. Since the pressure on the lungs increase rushing the air to outside, expiration is called a passive process.

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