Question

At high altitude, the RBC in human blood

• A. Increase in size.
• B. Decrease in size.
• C. Increase in number.
• D. Decrease in number.

Answer 1

Answer: (C)

Increase in number.

At high altitudes, there is a decrease in oxygen hemoglobin saturation. This hypoxic condition causes hypoxia-inducible factor 1 (HIF- 1) to become stable and stimulates the production of erythropoietin (EPO), a hormone secreted by the kidneys. EPO stimulates red blood cell production from bone marrow in order to increase hemoglobin saturation and oxygen delivery. Thus, the total number of RBC increases.