Describe the differences in composition between inspired and expired air, limited to: oxygen, carbon dioxide and water vapour

SouravNovember 14, 2024

Answer

The composition of inspired (inhaled) air and expired (exhaled) air differs significantly, particularly in terms of oxygen, carbon dioxide, and water vapor. Here’s a concise breakdown of these differences:

1. Oxygen (O₂)

• Inspired Air: Contains approximately 21% oxygen.
• Expired Air: Contains about 16% oxygen.
• Difference: The decrease in oxygen content in expired air is due to its absorption by the body during respiration for metabolic processes.

2. Carbon Dioxide (CO₂)

• Inspired Air: Contains about 0.04% carbon dioxide.
• Expired Air: Contains around 4% carbon dioxide.
• Difference: The increase in carbon dioxide in expired air results from its production as a waste product of cellular respiration, which then diffuses from the blood into the alveoli.

3. Water Vapor

• Inspired Air: Typically has a lower concentration of water vapor.
• Expired Air: Generally contains a higher concentration of water vapor.
• Difference: The increase in water vapor in expired air occurs because moisture evaporates from the moist surfaces of the respiratory tract and alveoli during exhalation, reflecting body temperature.