What is the Fluid Part of the Blood Called?

Blood Plasma is the massive river that carries everything else around the body. In fact, Plasma makes up about 55% of the total volume of your blood. Because it has to flow easily through tiny capillaries, Plasma is made up of 90% to 92% pure water. The remaining 8-10% is packed with dissolved proteins, salts, hormones, and nutrients.

While the Red Blood Cells (RBCs) have one single job (carrying oxygen), the fluid Plasma does almost everything else:

1. Nutrient Transport: After you eat food, the digested glucose and vitamins dissolve straight into the plasma to be delivered to starving muscles.
2. Waste Removal: It picks up toxic carbon dioxide and urea from the cells and carries them to the lungs and kidneys to be flushed out.
3. Heat Regulation: Because plasma is mostly water, it absorbs body heat from active organs (like the liver) and spreads it evenly across the body to keep you warm.

A common question in advanced biology exams is the difference between Plasma and Serum. Plasma contains crucial proteins called 'fibrinogens' that help the blood clot and form a scab when you get a cut. If you take Plasma and completely remove these clotting proteins from it, the remaining clear liquid is called Serum.