Question

People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude:

• A. people get pollution-free air to breathe and more oxygen is available
• B. atmospheric O₂ level is less and hence more RBCs are needed to absorb the required amount of O₂ to survive
• C. there is more UV radiation which enhances RBC production
• D. people eat more nutritive food, therefore more RBCs are formed

Answer 1

The Correct Option is B

At high altitudes, the partial pressure of oxygen in the atmosphere decreases. This means that there is less oxygen available in each breath, and as a result, the body needs to adapt to efficiently transport oxygen to its tissues. One way the body adapts is by producing more red blood cells (erythropoiesis).
More RBCs are needed to capture and transport the reduced oxygen available at high altitudes. This adaptation helps individuals living at high altitudes ensure their tissues receive an adequate oxygen supply. Therefore, the increase in RBC count is a physiological response to the lower atmospheric oxygen levels, not due to pollution-free air, UV radiation, or dietary factors.

So, the correct option is (B): atmospheric O₂ level is less and hence more RBCs are needed to absorb the required amount of O₂ to survive