What is serum in the context of blood?

Serum is defined as the clear, yellowish liquid that remains after blood has clotted and the clot has been removed. It consists of water, electrolytes, and various proteins, but lacks the cellular components of blood such as red blood cells, white blood cells, and platelets, which are found in whole blood. The process of coagulation leads to the formation of a clot, after which the liquid that remains is referred to as serum. This aspect distinguishes it from whole blood, which includes both the liquid and cellular components.

The other components, while relevant to blood composition, do not specifically define serum. Whole blood refers to blood in its entirety, before any separation has occurred. The protein-rich component of blood could refer to several fractions, such as plasma or serum albumin, but serum itself is specifically the fluid obtained after coagulation. Cellular elements pertain to the formed elements like red and white blood cells, which are not part of serum. Understanding serum in this manner is crucial for various laboratory analyses and medical applications.