Q145 / 180 · NEET 2016 (Phase 2) · Zoology

Lungs does not collapse between breaths and some amount of air will always remain in the lungs which can never be expelled because,

  • A
    There is a negative pressure in the lungs
  • Correct answer
    B
    There is a negative intrapleural pressure pulling at the lung walls
  • C
    There is a positive intrapleural pressure
  • D
    Pressure in the lungs is higher than the atmospheric pressure

Solution

The pressure within the pleural cavity is slightly less than that of atmospheric pressure and this is referred to as negative pressure. Hence, the lungs do not collapse between breaths and some air always remains in it. Even after the most forceful expiration, there will be sufficient volume of air in the lungs. This is called residual volume. It is about 1.2 litre in males and 1.1 litre in females.

Hence, the correct answer is option: 'B'.

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