In an average adult, approximately what percentage of whole blood is water?

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

Answer: (B)

Verified step by step guidance

1. Understand that whole blood is composed of plasma and formed elements (cells). The plasma portion contains a large amount of water, which makes up the majority of blood's volume.
2. Recall that plasma itself is about 90-92% water by volume, and plasma constitutes roughly 55% of whole blood volume in an average adult.
3. Recognize that the formed elements (red blood cells, white blood cells, and platelets) contain less water compared to plasma, but since plasma is the major component, the overall water content in whole blood remains high.
4. Combine these facts to estimate the total percentage of water in whole blood by considering the high water content of plasma and its proportion in blood.
5. Conclude that the approximate percentage of water in whole blood is around 80%, reflecting the dominant water content in plasma and its volume fraction in blood.