Solved UPSC CDS/OTA Question
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Q · Respiratory System medium · 45s
The primary site of gas exchange in the lungs is:
TopicRespiratory System
Question Typemultiple choice
Difficultymedium
Marking+1 / −0.33
Test Duration30 min
Step-by-Step Solution
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Alveoli are microscopic sac–like structures with extremely thin walls (one cell thick) and extensive capillary networks. Their large combined surface area—approximately 70 square meters in adults—facilitates rapid diffusion of oxygen into blood and carbon dioxide out of blood, making them the main sites for pulmonary gas exchange.
Final Answer: Option B - Alveoli