EasyZoologyBreathing and Exchange of Gases
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What is the site of actual gas exchange in the lungs?
A
Bronchi
B
Bronchioles
C
Alveoli
D
Trachea
Explanation
Alveoli are the tiny air sacs at the end of bronchioles where actual gas exchange (external respiration) occurs. They provide an enormous surface area (about 70 m² in humans) and are surrounded by a dense network of pulmonary capillaries. The alveolar walls are extremely thin (0.1–0.5 μm) to allow rapid diffusion of O₂ and CO₂.
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