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

Answer 1

The correct option is C atmospheric oxygen level is less and hence more RBCs are needed to absorb the required amount of oxygen to survive

Although the composition of air remains more or less the same at sea level and high altitudes, the density of air gradually reduces as one goes higher up. As a result, arterial p$O_2$ is also decreased. In order to survive, the body needs to take in a high amount of oxygen from the air, which is difficult, considering that the air has a low p$O_2$. The only solution to meet this need would be by producing more number of red blood cells in the body. Thus, people living at higher altitudes tend to have many more RBCs compared to people living at sea level.