Blood serum is a clear, yellowish liquid that remains after blood has clotted and all blood cells and clotting proteins have been removed. It acts as a transport medium, carrying various substances throughout the circulatory system.
Distinguishing Blood Serum
Blood serum differs from whole blood and plasma. Whole blood contains all its components: red blood cells, white blood cells, platelets, and plasma. Plasma is the liquid part of blood that includes clotting factors like fibrinogen, along with water, proteins, and dissolved substances. Plasma constitutes about 55% of total blood volume.
Serum is distinct because it is plasma from which clotting factors have been removed. When blood clots, fibrinogen and other clotting proteins are consumed. The remaining liquid is then separated from the clotted blood and cells, typically by centrifugation. This absence of clotting factors makes serum useful for diagnostic tests, as their presence could interfere with results.
Key Constituents of Serum
Blood serum contains a diverse array of molecules and ions. Proteins are abundant, constituting approximately 7% of its content. Albumin is the most prevalent, accounting for about 55% of total serum proteins, helping maintain fluid balance and transport small molecules like hormones and fatty acids. Globulins include immunoglobulins (antibodies) for defense, and alpha and beta globulins that transport lipids, hormones, and metal ions.
Electrolytes are also dissolved in serum. These electrically charged minerals, such as sodium, potassium, chloride, calcium, and bicarbonate, help regulate fluid balance, nerve impulses, muscle contractions, and maintain the body’s pH. Sodium and chloride are important for controlling fluid levels and blood pressure. Potassium supports nerve and muscle function, including heart activity.
Hormones, acting as chemical messengers, are transported through serum to their target organs and cells. Examples include insulin, which regulates blood sugar, and thyroid hormones, which influence metabolism. Nutrients like glucose, amino acids, and lipids are also carried in serum to provide energy and building blocks for cells. Waste products, such as urea and creatinine, are transported by serum to the kidneys and liver for excretion. Various enzymes are also present, some reflecting normal metabolic activity and others indicating tissue damage or disease.
Diagnostic Significance
The comprehensive composition of blood serum makes its analysis important for medical diagnostics. Measuring the concentrations of various constituents in serum provides insights into a person’s health status. Alterations in protein, electrolyte, hormone, or waste product levels can signal underlying health conditions. For example, elevated liver enzymes might suggest liver damage, while abnormal electrolyte levels could indicate kidney dysfunction or hormonal imbalances.
Serum tests are used to diagnose illnesses, monitor treatment effectiveness, and assess organ function. These tests provide information for identifying conditions like diabetes through glucose levels, assessing kidney health by measuring urea and creatinine, or evaluating thyroid function via hormone levels. Analyzing serum components offers a non-invasive way to detect physiological changes and guide medical interventions.