exuding

Transudation consists in the passage of a liquid, the so-called transudato, through a membrane; typical is the example of the liquid component of blood through the capillary wall.

By definition, the transudate is particularly poor in proteins and cellular elements; it differs in this sense from the exudate, in which an important solid component is recognized formed by plasma proteins, blood cells and substances deriving from the destruction or from the metabolic activity of the damaged tissue.

The exudate is therefore consequent to episodes of increased permeability of the capillary membrane, which can be traversed by solutes normally held within the bloodstream. Typical is the example of inflammatory phenomena (traumas, injuries of various kinds, infections, etc.). In the formation of the transudate, on the contrary, the capillary wall maintains the normal filtering capacity (there is no phlogistic component); the increased capillary and venous blood pressure plays a major role. Transudation is also favored by the low level of plasma proteins, as happens in hypoalbuminemia; due to the laws of osmosis (oncotic or colloid-osmotic pressure), in fact, the more the blood is rich in proteins and the more water it draws from the interstitial liquid, and vice versa. To cite an example, the abnormal accumulation of fluids in the abdominal cavity (ascites) is typical of both severe protein-calorie malnutrition (Kwashiorkor), and of all conditions associated with portal hypertension, such as cirrhosis.

In women, the so-called "vaginal secretions" that lubricate the canal during sexual arousal, are formed by transudate, since this tract - unlike the external opening and the cervix - is devoid of glands.