Question

A large proportion of oxygen is left unused in the human blood even after its uptake by the body tissue. This $O_2$

• A. Helps in releasing more $O_2$ to the epithelium tissues.
• B. Acts as a reserve during muscular exercise.
• C. Raises the $PC{O}_2$ of blood to 75 mm of Hg.
• D. Is enough to keep oxyhaemoglobin saturation at 96%.

Answer 1

Answer: (B)

Acts as a reserve during muscular exercise.

The difference in the oxygen content of blood between the arterial blood and the venous blood is known as the the arteriovenous oxygen difference. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body. Arterial blood contains an oxygen concentration of around 20 mL/100 mL. Venous blood has an oxygen concentration of 15 mL/100 mL. Therefore the arterio-venous difference is around 5 mL/100 mL at rest. During intense exercise, however, the difference can increase to as much as 16 mL/100 mL due to the working muscles extracting more oxygen from the blood than they do at rest.