Biology Respiration / Gaseous Exchange MDCAT 2017
PMDC Verified Question 25 of 34
Site of gaseous exchange in humans is:
A
Alveoli
B
Bronchus
C
Trachea
D
Nose
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Alveoli
Concept: Gaseous exchange requires a thin, moist, and highly vascularized surface to allow efficient diffusion of respiratory gases.

Solution:
  • The alveoli are microscopic, balloon-like air sacs at the terminal ends of the respiratory tree.
  • They consist of a single layer of squamous epithelial cells surrounded by a dense network of pulmonary capillaries.
  • This creates an optimal, extremely thin barrier for the rapid diffusion of \( \text{O}_2 \) and \( \text{CO}_2 \).


Why other options are incorrect:
  • Trachea, Bronchus, Nose: These form the conducting zone of the respiratory system. Their thick walls and structural cartilage prevent any meaningful gas exchange. They only filter, warm, and humidify the air.

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.

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