What is the osmotic pressure?

One of the terrible diseases, carried off hundreds of thousands of lives, was cholera. In the last stage of the human body due to the continuous loss of water vomiting and diarrhea becomes a sort of a mummy. Man dies, because the tissue it cannot live without the necessary amount of water. To enter the liquid through a mouth it is impossible, for she immediately thrown back because of uncontrollable vomiting. Doctors have long had an idea: to enter the water directly into the blood in the vessels. However, to solve this task was then, when it was understood phenomenon known as osmotic pressure.
We know that the gas, being in a particular vessel, the pressure on its walls, in an effort to take the greatest possible extent. The more gas is compressed, i.e. the more particles it is enclosed in this space, the greater the pressure. It turned out that the substances dissolved, for example, in water, in a sense similar gases: they also tend to take the greatest possible volume, and the concentration of the solution, the more the strength of this commitment. What's is the property of solutions? That they greedily "attract" more solvent. Quite to the solution of salt, add a little water, and the solution quickly becomes even, he kinda sucks up the water, thus increasing its volume. Described property of a solution to attract solvent is called osmotic pressure.
If we put the red blood cells in a clean glass of water, they quickly "will swell and burst. It is clear: the protoplasm of erythrocytes is a solution of salts and proteins certain concentration that has osmotic pressure much more than pure water, where there is little salt. Therefore, erythrocyte and "passive" to find water. If we place the erythrocytes in a very concentrated salt solution, they will shrivel - osmotic pressure of a solution will be higher, it will "suck" water from the red blood cells. Like the red blood cells behave and other cells of the body.
It is clear that the introduction of fluid in the bloodstream, it should have a concentration corresponding to their concentration in the blood. The experiments revealed that such is the 0.9 %solution of sodium chloride. This solution has been called physiological.
Introduction 1-2 liters of such solution intravenously dying kholernomu patient had literally miraculous effect. The man on eyes "alive", sat in bed, asked is, and so on, Repeating the introduction of a solution 2-3 times a day, helping the body to overcome the most difficult period of the disease. Such solutions containing a number of other substances, apply now for many diseases. In particular, it is very important krovezameschayuschih solutions in a time of war. Blood loss is terrible not only because it deprives the body of red blood cells, but, above all, that disturbed function of the cardiovascular system, "minded" to work with a specific amount of blood. Therefore, in cases when, for one reason or another a blood transfusion is not possible, a simple physiological solution can save the life of a wounded.
Knowledge of the laws of osmotic pressure is of great importance, because it helps regulate water metabolism of the body. So, it becomes clear why salty foods cause thirst: the excess salt increases the osmotic pressure of our tissues, ie, the "greed" them to the water. Therefore, patients with edema give less salt, so as not to retain water in the body. On the contrary, the workers of hot shops, losing a lot of water, it is necessary to pour salt water, because then they emit and salt, are deprived of them. If in these cases, people will drink clean water, greed tissues to water will be reduced, and this will increase perspiration. The condition of the body will be dramatically worse.