How is alveolar air different from inspired air in the human respiratory system?

• A. Alveolar air contains a higher concentration of oxygen (\(\mathrm{O_2}\)) and a lower concentration of carbon dioxide (\(\mathrm{CO_2}\)) compared to inspired air.
• B. Alveolar air contains no nitrogen (\(\mathrm{N_2}\)), while inspired air is mostly nitrogen.
• C. Alveolar air and inspired air have identical concentrations of oxygen and carbon dioxide.
• D. Alveolar air contains a higher concentration of carbon dioxide (\(\mathrm{CO_2}\)) and a lower concentration of oxygen (\(\mathrm{O_2}\)) compared to inspired air.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the difference between alveolar air and inspired air. Inspired air is the air that enters the lungs from the external environment, while alveolar air is the air present in the alveoli, where gas exchange occurs between the lungs and blood.
2. Step 2: Recognize the role of gas exchange in the alveoli. Oxygen (\(\mathrm{O_2}\)) from inspired air diffuses into the blood, while carbon dioxide (\(\mathrm{CO_2}\)) from the blood diffuses into the alveoli. This process alters the composition of alveolar air compared to inspired air.
3. Step 3: Compare the concentrations of gases. Inspired air typically contains a higher concentration of oxygen (\(\mathrm{O_2}\)) and a lower concentration of carbon dioxide (\(\mathrm{CO_2}\)). In contrast, alveolar air has a lower concentration of oxygen (\(\mathrm{O_2}\)) and a higher concentration of carbon dioxide (\(\mathrm{CO_2}\)) due to gas exchange.
4. Step 4: Address the misconception about nitrogen (\(\mathrm{N_2}\)). Both inspired air and alveolar air contain nitrogen (\(\mathrm{N_2}\)), as nitrogen is not significantly involved in the gas exchange process in the lungs.
5. Step 5: Conclude that the correct answer is: Alveolar air contains a higher concentration of carbon dioxide (\(\mathrm{CO_2}\)) and a lower concentration of oxygen (\(\mathrm{O_2}\)) compared to inspired air, due to the process of gas exchange in the alveoli.