What makes up approximately 55% of the total volume of whole blood?

Plasma is the component that makes up approximately 55% of the total volume of whole blood. It is a pale-yellow liquid that consists mostly of water, but also contains proteins, electrolytes, nutrients, hormones, and waste products. The primary function of plasma is to transport various substances throughout the body, including nutrients to cells, hormones to target organs, and waste products to the kidneys for excretion. Additionally, plasma plays an essential role in maintaining blood pressure and regulating body temperature.

In contrast, red blood cells, white blood cells, and platelets each contribute to the cellular components of blood, accounting for about 45% of the total blood volume. Red blood cells are critical for oxygen transport, white blood cells are involved in immune responses, and platelets are essential for blood clotting. Therefore, while all components are vital for bodily functions, plasma is the predominant component by volume.