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JAMB Biology 2006 Question 5

Question 5

Respiration

An increase in air pressure in the lungs is due to the

  1. A.increase in the volume of the thoracic cavity
  2. B.upward movement of the ribs
  3. C.relaxation of the diaphragm
  4. D.contraction of intercostal muscles
Show the answer and explanation

Answer: C (relaxation of the diaphragm)

Explanation

When the diaphragm relaxes it domes upward and the chest gets smaller. The smaller volume raises the air pressure in the lungs, pushing air out.