Vessels and swelling
Between cells in the intercellular environment is containeda so-called tissue fluid that washes all the cells of the body. Normally, through the capillaries, there is a constant exchange between the tissue fluid and the blood fluid. The passage of fluid from the vessels into the surrounding tissue or to its surface is called transudation, and the liquid itself is called the transudate.
The transudate (edematous fluid) containsrelatively little protein (up to 2%) and individual uniform elements of blood than its composition and differs from the composition of the exudate (see "Inflammation", p. 41). If a large amount of fluid is released into the surrounding tissue and for some reason it is not absorbed back, it will be swelling. By origin (pathogenesis), edema is divided into mechanical, osmotic and oncotic.
Mechanical edema is caused by increasedpressure in small vessels and capillaries. Such edema is observed mainly in venous stasis, in which the walls of the vessels are stretched and their permeability increases.
Due to the difference in pressure between the blood and the tissue fluid, the fluid from the vessels begins to seep into the surrounding tissue.
Stagnant swelling is local and general. With thrombosis or compression of a large vein, there is a local edema, and with a decrease in cardiac activity, a general swelling develops. It begins with the lower and farthest from the heart parts of the body: first the swelling of the feet, then the legs and thighs. The edematous fluid appears in the abdominal cavity, the pleura, etc. The swelling in the body cavities - the abdominal, pleural, pericardial cavity, etc. - is called dropsy. A dropsy of the abdominal cavity is called ascites.
Osmotic edema is due to the differencein the osmotic pressure between the blood and the tissue fluid. It is known that if solutions of salts with different concentrations are separated by a thin animal septum (in this case, by the wall of the capillary), then the water from the less concentrated solution will gradually percolate into a more concentrated one until the complete equation of their concentration. If the solution of salts in the tissues is higher than in the blood, then the liquid will flow from the blood into the tissue
With inflammation of the kidneys, when they are isolated fromthe body lacks salts, primarily sodium chloride (sodium chloride), these salts accumulate in the tissues and fluid from the blood rushes into the surrounding tissue.
Oncotic, or colloidal, swelling occurs as a result of an incorrect correlation of colloids between blood and tissue fluid.
Colloids are organic substances,which in water do not dissolve, but swell. Such substances, for example, include starch and protein. With some forms of kidney disease, when the latter produce a large amount of protein, the blood impoverishes protein and water from it passes into interstitial spaces. Thus, with kidney diseases, osmotic and oncotic edema are noted. With the distribution of renal edema, gravity and distance from the heart do not play a role. Therefore, renal edema is evenly distributed throughout the body.
Under the skin, renal edema first appear in places with the most loose subcutaneous tissue, for example on the face, near the eyes.
Hungry cachectic edema can also be attributed to oncological, since fasting in blood significantly reduces the protein content.
Neurotic edema is caused bydefeat co-sudodvigatelnyh nerves, causing a sharp widening of blood vessels and increase their permeability. The capillary is a significant stagnation of the blood, and hence local increase in blood pressure, so the pathogenesis of edema likely can be attributed to mechanical.
Toxic edema can result from poisoning of tissues with poisons. The mechanism of their appearance is associated with the defeat of the vascular walls and the nerve endings embedded in them.
This toxic edema approachesinflammatory edema (see "Inflammation", p. 41). Toxic include swelling caused by food, medicinal and other substances, for example poisons with insect bites. These include hives and swelling with serum sickness. Often such edemas are a manifestation of an allergic reaction (increased sensitivity), not only to various poisons, but also to other substances (see "Allergies", p. 24).
To toxic swelling should also be attributed to pulmonary edema when the poisoning agents are strangled with asphyxiating effects (chlorine, phosgene, diphosgene, etc.).