Introduction
Blood plasma is the liquid portion of blood that serves as a transport medium for transferring rich nutrients to the different cells of the various body organs and for transporting waste products obtained from the metabolism of the cells to the kidneys, lungs, and liver for expelling out of the body. Blood plasma also transports the blood cells. It plays a crucial role in regulating normal blood pressure. Plasma helps to maintain homeostasis by distributing heat throughout the body. It also helps in maintaining biological stability, including acid-base balance in the blood as well as the body. The source of the origin of plasma, which constitutes about 55 % of whole blood, is quite interesting since no organ synthesizes it. On the contrary, it is primarily formed from water and salts that are mainly absorbed through the digestive tract.
What Is the Composition of Blood Plasma?
Plasma is derived from the blood when all the types of blood cells, including red blood cells, white blood cells, and blood platelets, are isolated from whole blood. The remaining fluid is straw-colored and comprises 90 to 92 % water. However, this fluid contains solutes that are critical and necessary to sustain health and life. Important components include electrolytes such as sodium, potassium, chloride, bicarbonate, magnesium, and calcium. There are traces of other substances, including amino acids, minerals, vitamins, proteins, organic acids, and enzymes. Several hormones like insulin, corticosteroids, and thyroxine are also found in the blood plasma. These hormones are secreted into the blood by the endocrine system. The concentration of hormones in the blood plasma should be carefully regulated for good health. Nitrogenous wastes like carbamide (urea) and creatinine are also found in the blood plasma and transported to the kidney for excretion.
Plasma contains approximately 91 % to 92 % of water and eight to nine percent of solids. It mainly comprises:
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Coagulants (clotting factors), mainly fibrinogen, help in blood clotting.
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Plasma proteins, such as serum albumin and serum globulin, help regulate the colloidal osmotic pressure at about 25 millimeters of mercury.
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Electrolytes such as sodium, potassium, bicarbonate, magnesium, chloride, and calcium help to maintain the pH of the blood.
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Immunoglobulin proteins help fight against infection.
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Various other minute amounts of enzymes, hormones, minerals, and vitamins.
What Is the Clinical Significance of the Plasma Components?
Plasma consists of six to eight percent proteins. Each of them has a clinical significance of its own.
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Coagulation Proteins- The coagulation proteins are one of these. The fibrinogen protein that is circulating in the blood is converted to fibrin when blood clotting is activated, trapping the cellular components of the blood. The remaining liquid, which is devoid of cells and fibrinogen, is called serum. Fibrinogen helps in blood clotting.
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Serum Albumin- Serum albumin is a protein synthesized by the liver that comprises about 60 percent of all plasma proteins. Apart from maintaining osmotic pressure in the blood vessels, it is also a pivotal carrier protein for various substances, including hormones.
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Alpha and Beta Globulins- There are other proteins known as alpha and beta globulins that transport lipids like fatty cholesterol along with steroid hormones, glucose, and serum iron.
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Immunoglobulins- The immunoglobulins (gamma globulins) are secreted by B- lymphocytes (bursa-derived) of the immune system. They include protective antibodies that are synthesized in response to infectious agents.
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Cytokines- Cytokines are proteins produced by cells of different organs, immune cells, and bone marrow in order to maintain normal hematopoiesis (blood cell synthesis) and mediate inflammation.
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Complement System- Complement is another protein component in the blood plasma that is important in regulating immune and inflammatory responses to various viral and bacterial antigens.
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Glucose (Sugar)- High or low glucose (sugar) concentrations in the plasma or serum usually help to confirm serious diseases such as diabetes mellitus and hypoglycemia (a condition where the blood sugar level is lower than normal).
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Tumor Markers (Biomarkers)- Substances that are secreted into the plasma by certain malignant tumors may indicate an occult (hidden) malignancy (cancer). For example, a higher concentration of prostate-specific antigen (PSA) in an elderly asymptomatic person may be suggestive of undiagnosed prostate cancer.
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Alpha-1 Antitrypsin- Alpha-1 antitrypsin is an enzyme synthesized in the liver that plays a crucial role in the lungs by increasing the concentration of proteases which helps to counteract the effect of elastases. Elastases are synthesized by the neutrophils in response to inflammatory reactions such as smoking.
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Electrolytes-The electrolytes, like potassium and acid-base systems in the plasma, are precisely regulated. Therefore, a slight increase in plasma potassium levels can result in death. Similarly, an imbalance in sodium, chloride, bicarbonate, calcium, and magnesium levels in the plasma should be regulated within a narrow range. Smaller molecules like sodium, potassium, sugar, and calcium are mainly responsible for the concentration of soluble plasma particles.
Conclusion:
Blood plasma is mainly used to transport rich nutrients to the different cells of the various organs of the body and deliver waste nitrogenous products that are generated through cellular metabolism to the excretory system (kidneys), pulmonary system (lungs), and liver for elimination. The plasma consists of various components that are clinically significant in various fields. Plasma testing of the various plasma constituents is usually carried out to diagnose and confirm disorders like diabetes that are dependent on serum glucose levels or von Willebrand disease. Monitoring of plasma prothrombin levels is required in patients who are on anticoagulants. Therefore, plasma constituents are important because of their pathophysiological and clinical significance.
