What is the fluid component of blood called?

The fluid component of blood is called plasma. Plasma is a yellowish liquid that constitutes about 55% of total blood volume. It serves several essential functions, including transporting nutrients, hormones, and proteins to the various parts of the body. Plasma also helps maintain blood pressure and regulates body temperature.

In contrast, serum is the fluid that remains after blood has clotted and does not contain clotting factors. Hemoglobin is a protein found within red blood cells that binds oxygen for transport throughout the body, and interstitial fluid is the extracellular fluid surrounding the cells in tissues, providing a medium for the exchange of materials between blood and cells. Therefore, plasma stands out as the correct answer, as it is the primary fluid component of blood responsible for various transport and regulatory functions.