Approximately what percentage of whole blood is water?

• A. About 50%
• B. About 95%
• C. About 20%
• D. About 80%

Answer: (D)

Verified step by step guidance

1. Understand that whole blood is composed of plasma and formed elements (cells like red blood cells, white blood cells, and platelets).
2. Recognize that plasma, the liquid portion of blood, makes up about 55% of whole blood by volume.
3. Know that plasma itself is approximately 90-92% water, with the rest being proteins, electrolytes, and other solutes.
4. Calculate the approximate percentage of water in whole blood by multiplying the percentage of plasma by the percentage of water in plasma: \$0.55 \times 0.90 = 0.495$ (or about 49.5%).
5. Consider that the water content in the formed elements also contributes slightly to the total water content, raising the overall water percentage in whole blood to about 80%.