Question

What is the approximate normal composition of alveolar air?

• A. 14% oxygen, 6% carbon dioxide, 80% nitrogen
• B. 21% oxygen, 2% carbon dioxide, 77% nitrogen
• C. 16% oxygen, 3% carbon dioxide, 81% nitrogen
• D. 10% oxygen, 8% carbon dioxide, 82% nitrogen

Answer 1

The correct option is A 14% oxygen, 6% carbon dioxide, 80% nitrogen

The gaseous exchange occurs directly between blood and lung alveoli. The approximate percentage of gases in alveolar air are oxygen: 13-14%, carbon dioxide: 5-6%, nitrogen: 79% and the air is saturated with water vapour.

In inhaled air, oxygen content: 20%, carbon dioxide: 0.04%, nitrogen: 79% and the water vapour content is variable.

Therefore, the correct answer is option A.