The number of alveoli in human lungs is estimated to be around:_________?
Correct answer: B. 500 millions
- A. 150 millions
- B. 500 millions
- C. 800 millions
- D. 1 billion
Explanation
Human lungs contain roughly 300 to 500 million alveoli, so 500 million is the closest estimate given. Alveoli greatly increase the surface area for diffusion of oxygen and carbon dioxide. Students may choose 800 million because estimates vary, but 500 million is the standard approximate figure in many textbooks.
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About Gaseous Exchange in Lungs
Gaseous exchange in the lungs occurs across the thin, moist alveolar and capillary surfaces, where oxygen and carbon dioxide diffuse down partial pressure gradients. The topic covers alveolar adaptations, ventilation, the role of haemoglobin in oxygen transport, carbon dioxide carriage, and the difference between external gas exchange and cellular respiration.
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