Approximately how many erythrocytes (red blood cells) are present in a typical drop of blood?

• A. About 2.5 billion erythrocytes
• B. About 250 million erythrocytes
• C. About 2.5 million erythrocytes
• D. About 25,000 erythrocytes

Answer: (B)

Verified step by step guidance

1. Understand that erythrocytes, or red blood cells, are extremely numerous in blood, and their concentration is typically measured in millions per microliter (µL) of blood.
2. Recall that a typical drop of blood is approximately 50 microliters (µL) in volume, though this can vary slightly depending on the source.
3. Know that the average erythrocyte count in human blood is about 5 million cells per microliter (µL).
4. Calculate the total number of erythrocytes in one drop of blood by multiplying the erythrocyte concentration by the volume of the drop: \$5,000,000 \times 50$.
5. Interpret the result to estimate the number of erythrocytes in a typical drop of blood, which should be on the order of hundreds of millions.