What is the Function of Plasma Protein in Maintaining Blood Volume?

Blood volume regulation is a complex process that largely depends on plasma contents. Plasma proteins, in particular, have an important role because of the pressure ("oncotic pressure") they exert on small blood vessels.

Plasma Description

• Plasma is the liquid portion that remains after cells are removal from whole blood. According to the American Association of Blood Banks, plasma consists of water (90 percent), electrolytes (salts), metabolic products and proteins.

Plasma Proteins

• Plasma proteins include albumin, clotting factors, immunoglobulins (antibodies) and other globulins, such as fibrinogen.

Functions & Effects

• Plasma proteins contribute to blood flow regulation via the oncotic pressure they exert. A low plasma protein content (low oncotic pressure) can cause fluid to build up in the tissues, resulting in edema. Conversely, normal or high oncotic pressure keeps fluid in the blood vessels.

Albumin Functions

• Albumin provides most of the pressure needed to pull water back from the tissues to the blood vessels. According to the Merck Manuals of Medical information, it helps maintain blood volume by preventing fluid leakage from blood vessels into tissues.

Fibrinogen and Clotting Factors

• Stedman's medical dictionary describes fibrinogen as the only coagulable plasma protein. Along with clotting factors, it is essential to normal blood clotting. Normal blood clotting helps maintain blood volume by controlling bleeding.

Immunoglobulins

• Immunoglobulins are plasma proteins that help defend the body against disease-causing organisms. They don't have a significant role in blood volume regulation.