Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because
Answer: (B) There is a negative intrapleural pressure pulling at the lung walls. Answer: (b) There is a negative intrapleural pressure pulling at the lung walls Solution: The lungs sit in an air-tight thoracic chamber and are held expanded by the sub-atmospheric (negative) intrapleural pressure that pulls outward on the lung walls, so they never fully collapse and some air (residual volume) always remains.
- A.There is a negative pressure in the lungs
- 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
Correct Answer
(B) There is a negative intrapleural pressure pulling at the lung walls
Solution & Explanation
Answer: (b) There is a negative intrapleural pressure pulling at the lung walls Solution: The lungs sit in an air-tight thoracic chamber and are held expanded by the sub-atmospheric (negative) intrapleural pressure that pulls outward on the lung walls, so they never fully collapse and some air (residual volume) always remains. A positive or higher-than-atmospheric pressure would expel air and collapse the lungs, so the cause is the negative intrapleural pressure. NCERT: Ch 14, p.185, line 39 — "there is a negative pressure in the lungs with respect to atmospheric pressure"