PMDC Verified Question 21 of 34
During inspiration, the space inside the chest cavity is increased due to:
A
The contraction of the muscles of the diaphragm
B
The relaxation of the muscle of the diaphragm
C
Relaxation of the external intercostal muscle
D
Increased pressure
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: The contraction of the muscles of the diaphragm
Concept: Boyle's Law states that pressure is inversely proportional to volume. Inspiration requires a volume increase to drop internal pressure below atmospheric pressure.

Solution:
  • During active inspiration, the nervous system signals the skeletal muscles of the respiratory pump.
  • The diaphragm contracts, causing its dome shape to flatten and move downward.
  • Simultaneously, the external intercostal muscles contract, lifting the rib cage. These combined muscle contractions dramatically increase the volume of the chest cavity.


Why other options are incorrect:
  • Relaxation of diaphragm / intercostals: This occurs during expiration, reducing chest cavity volume.
  • Increased pressure: Volume must increase to decrease pressure for inspiration to occur.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.