Serum (blood) small molecules to cells. Like many other mass nouns, the word "serum" can be pluralized when used in certain senses. To speak of multiple serum specimens from multiple people (each with a unique population of antibodies), physicians sometimes speak of sera (the Latin plural, as opposed to *"serums"). Serum (blood) In blood, the serum () is the component that is neither a blood cell (serum does not contain white blood cells- leukocytes, or red blood cells- erythrocytes), nor a clotting factor; it is the blood plasma not including the fibrinogens. Serum includes all proteins not used in blood clotting and
Blood plasma Blood plasma Blood plasma is a yellowish coloured liquid component of blood that normally holds the blood cells in whole blood in suspension; this makes plasma the extracellular matrix of blood cells. It makes up about 55% of the body's total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside cells). It is mostly water (up to 95% by volume), and contains dissolved proteins (6–8%) (i.e.—serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na, Ca, Mg, HCO, Cl, etc.), hormones, carbon dioxide (plasma being the main medium for excretory product transportation) and oxygen.