What percentage of total blood volume does plasma constitute?

Plasma constitutes approximately 55% of total blood volume in a healthy adult. This pale yellow liquid is primarily composed of water, which makes up about 90% of its volume. The remaining 10% consists of various solutes, including proteins (like albumin and globulins), electrolytes, nutrients, hormones, and waste products.

Understanding plasma's role is crucial, as it serves as the medium for transporting cells, nutrients, and waste products throughout the body. It also plays a vital role in maintaining blood pressure and regulating body temperature due to its fluid nature.

The other choices do not accurately represent the proportion of plasma in blood volume. For example, 40% and 45% are below the established norm, while 50% is a reasonable estimate but still underestimates the typical percentage found in adult blood composition. Therefore, the most accurate answer is that plasma makes up about 55% of the total blood volume.