Biology Respiration / Gaseous Exchange SZABMU 2024
PMDC Verified Question 2 of 34
When the diaphragm muscle lowers and the ribs move outward and forward, the volume of ________ increases, and the pressure on ________ decreases respectively.
A
Abdominal cavity, lungs
B
Chest cavity, lungs
C
Lungs, chest cavity
D
Lungs, abdominal cavity
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Chest cavity, lungs
Concept: Inspiration is driven by Boyle's Law: an increase in container volume produces an immediate drop in internal pressure.

Solution:
  • When the diaphragm contracts (lowers) and intercostal muscles elevate the ribs, the physical dimensions of the chest cavity expand.
  • Because the chest cavity volume increases, the intrapleural pressure plummets.
  • This vacuum-like effect pulls on the lungs, causing their internal intrapulmonary pressure to decrease below atmospheric levels, sucking air in.


Why other options are incorrect:
  • Abdominal cavity: When the diaphragm lowers, it actually compresses the abdominal cavity, decreasing its volume and increasing abdominal pressure.
  • Lungs, Chest cavity (reversed): The structural volume of the chest cavity dictates the pressure applied to the lungs, not vice versa.

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.

Previous Question All Respiration / Gaseous Exchange MCQs Next Question

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.

Enter Arena Sprint iOS App Android App