What is plasma?

Structure and Functions

A clear, straw-colored liquid, plasma makes up about 55 percent of the total blood volume. Although its major component is water (90 percent by volume), plasma also contains glucose, proteins, clotting factors, hormones, carbon dioxide, and dissolved salts and minerals. The main proteins in plasma are albumin, globulins, and clotting proteins, particularly fibrinogen. Gamma globulin is an important component of the immune system. Mineral ions in plasma include sodium, potassium, chloride, bicarbonate, calcium, and magnesium. These electrolytes are essential in maintaining fluid balance, nerve conduction, muscle contraction, blood clotting, and pH balance in the body.

Suspended within the plasma are red blood cells (erythrocytes), five kinds of white blood cells (leukocytes), and platelets (thrombocytes). In addition to carrying these blood cells, plasma transports nutrients, waste products, antibodies, clotting agents, and chemical messengers to help maintain a healthy body. Plasma circulates dissolved nutrients throughout the body, where they are diffused by osmotic pressure into the tissues and cells that need them. It is also the main medium for transporting excretory products to the kidneys and lungs for elimination.

Disorders and Diseases

The most characteristic disease associated with plasma is hemophilia. It results from an inherited change in one of the clotting proteins (factor VIII), leaving it dysfunctional. This single change disrupts the chemical reactions necessary for clotting. As a result, patients with hemophilia experience bleeding, swelling, and bruising. Crippling defects may include recurrent hemorrhaging into joints and muscles and bleeding into body cavities.

Tests of the clotting function of plasma include analysis of indicators such as the prothrombin time and the partial thromboplastin time. These tests identify a deficiency of any of the clotting factors. Most cases involving abnormal bleeding can then be traced to specific defects. Hemophilia can be controlled by infusion of factor VIII that has been collected from donated blood or plasma.

Perspective and Prospects

The possibility of using blood plasma for transfusion purposes was reported in a medical journal by physician Gordon R. Ward in 1918. Due to the advantages that plasma has over whole blood with regard to shelf life and donor-recipient compatibility, the use of plasma for blood transfusions was advanced during the 1930s. During World War II, anatomist Charles Drew developed a modern, highly sterile system for processing, testing, and storing plasma in a blood bank. During the early twenty-first century, research suggests that exploring and measuring the plasma proteome (the proteins in plasma, of which there are known to be 289) can help track slow changes associated with disease, such as rheumatoid arthritis. The best therapeutic options and drugs available for treatment of the disease can then be implemented.

Bibliography

Berenson, James R. "Overview of Plasma Cell Disorders." Merck Manual Home Health Handbook, July 2008.

De la Rocha, Kelly, Igor Puzanov, and Brian Randall. "Plasmapheresis." Health Library, May 11, 2013.

"Hemophilia." MedlinePlus, June 26, 2013.

Schaller, Johann, et al. Human Blood Plasma Proteins: Structure and Function. New York: Wiley, 2008.

Trice, Linda. Charles Drew: Pioneer of Blood Plasma. New York: McGraw-Hill, 2000.

Valverde, José Luis, ed. Blood, Plasma, and Plasma Proteins: A Unique Contribution to Modern Healthcare. Amsterdam: IOS Press, 2006. Pharmaceuticals Policy and Law 7.