Oncotic Pressure

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oncotic pressure

[äŋ′käd·ik ′presh·ər]
Also known as colloidal osmotic pressure.
The osmotic pressure exerted by colloids in a solution.
The pressure exerted by plasma proteins.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Oncotic Pressure


the component of osmotic pressure that is contributed by substances of high molecular weight in a solution.

In human blood plasma, oncotic pressure ranges from 3 to 4 kilonewtons per square meter, or from 0.03 to 0.04 atmospheres; this constitutes only about 0.5 percent of the total osmotic pressure. Nevertheless, oncotic pressure plays a major role in the formation of some of the body’s fluids, including the intercellular fluid and capsular urine.

The walls of capillary blood vessels are readily permeable to water and substances of low molecular weight, but not to proteins. The filtration rate of fluid through the capillary wall is determined by the difference between the oncotic pressure, which is contributed by plasma proteins, and the blood’s hydrostatic pressure, which is a function of the heart. The saline solution at the arterial end of the capillary passes into the intercellular space together with nutrients. At the venous end of the capillary the process takes place in the opposite direction, since venous pressure is lower than oncotic pressure, and substances that are eliminated by the cells pass into the blood (see).

The oncotic pressure diminishes in diseases that involve a decrease in the concentration of blood proteins—especially albumins. This pressure decrease may be one of the reasons why fluid accumulates in the intercellular space and causes edema.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In its complex composition, blood provides perfectly balanced components as well as the most suitable oncotic pressure.
This is likely related to the significant haemodynamic changes which occur in the postpartum period, including 65% increase in cardiac output, acute blood loss at delivery and a decrease in plasma protein oncotic pressure, which may exacerbate symptoms in patients with underlying cardiovascular or pulmonary dysfunction.
Histological changes in TC are characterized by moderately increased production of extracellular matrix, mild neutrophil infiltration and disorganization of contractile and cytoskeletal proteins but not by apoptotic or oncotic cell death (29).
They are (1) hydrostatic pressure inside the glomerular capillaries, also known as glomerular hydrostatic pressure ([P.sub.G]), which exerts 60 mmHg in favor of filtration, (2) hydrostatic pressure in Bowman's capsule (PB) that equals about 18 mmHg opposing the filtration, and (3) colloid osmotic pressure of the glomerular capillary plasma proteins, also known as glomerular oncotic pressure ([[pi].sub.G]), which shows 32 mmHg acting against the filtration.
On reperfusion, the generation of reactive oxygen species (ROS), rapid reintroduction of adenosine triphosphate in the presence of elevated [[[Ca.sup.2+]].sub.i], and induction of the mitochondrial permeability transition lead to hypercontracture as well as apoptotic and oncotic cell death [2].
Schlossman, "Molecular cloning of porimin, a novel cell surface receptor mediating oncotic cell death," Proceedings of the National Acadamy of Sciences of the United States of America, vol.
The process of edema formation has been explained by many different mechanisms with some postulating edema to be caused by imbalance in oncotic pressure or result from BBB disruption by inflammation.
It is also responsible for the normal colloid oncotic pressure and therefore severe hypoalbuminemia causes generalized edema.
(1998) reported that blood hyper viscosity, elevation in oncotic pressure, vasculitis and platelet dysfunction were important in pathogenesis of ocular bleeding observed in dogs.
The aim of massive transfusion is to replace the volume lost, provide hemostasis, and correct the O2 carrying capacity and plasma oncotic pressure.
In nephrotic syndrome, low oncotic pressure can result in reduced renal perfusion and reversible acute tubular injury [25].
Drinking plenty of fluids and limiting salt intake keeps your kidneys healthy and also decreases the oncotic (inside the vessel) pressure of the blood.