The osmotic pressure of blood

If two solutions, one of which is more concentrated, that is, it contains more solute than the second, separated by a semi-permeable membrane, letting a solvent such as water but do not let the dissolved substance, the water becomes more concentrated solution. The force that causes the movement of a solvent through a semipermeable membrane, called osmotic pressure.
Osmotic pressure of a solution can be measured using osmometer. The latter consists of two vessels, separated by a semi-permeable membrane. One of these vessels is poured more concentrated solution of any substance, and another with a less concentrated solution or clean solvent. The first of these vessels turning cap, which is the vertical gauge tube. The solvent is transferred to the vessel with a more concentrated solution, and the liquid goes in the side of the tube. The pressure of water column expresses the osmotic pressure.
The osmotic pressure of blood, lymph and is of great importance in the regulation of water exchange between the blood and the tissues. The change of osmotic pressure of the fluid surrounding the cells, leads to violations of water metabolism in them. This can be seen on the example of red blood cells, which, being immersed in a solution of NaCl, with great osmotic pressure than the blood plasma, lose water, have sharply reduced in volume and shrink. Red blood cells placed in NaCl solution with a lower osmotic pressure, on the contrary, swell, increase in volume and eventually deteriorate.
The osmotic pressure of the blood may be defined cryoscopes, i.e. by measuring the temperature of freezing. As is known, the freezing point of the solution is lower the higher its osmotic pressure, i.e. more than total concentration in the solution of the molecules, ions and colloidal particles.
The lowering of the freezing point below 0 deg (Delta t degrees), in other words depression, odnomernogo aqueous electrolyte is 1,85 deg and osmotic pressure of such a solution is 22.4 ATM. Knowing the freezing point of the investigated solution, you can calculate the value of its osmotic pressure.
A person depression of blood equal to 0.56-0,58 deg and consequently, the osmotic pressure is equal to 7.6 - 8.1 ATM. About 60% of this pressure is the share of NaCl. The osmotic pressure of the red blood cells and other cells of the body is the same as the surrounding fluid.
The osmotic pressure of the blood of mammals and man held relatively constant level, as illustrated by the following experience. In the vein of the horse was introduced 7 l 5% solution of sodium sulfate, what on calculation should increase the osmotic pressure of blood plasma in 2 times. However, after 10 minutes of osmotic pressure of plasma returned almost to normal, and after 2 hours it was perfectly normal. This was due to the removal of a significant amount of salts with urine, liquid feces and saliva. The allocations contained not only introduced sulphates and chlorides and carbonates; sulphates same can be detected in the blood after osmotic pressure became normal. This shows that in the body in the first place, restored normal osmotic pressure and only later the constancy of the ion composition of blood. The constancy of the osmotic pressure of blood is relative, because the body always occur small fluctuations due to a shift from the blood into tissue macromolecular substances (amino acids, fats, carbohydrates) and receipts from the tissues into the blood of low molecular weight products of cellular metabolism.
Excretory organs, mainly kidneys and sweat glands, are the regulators of osmotic pressure. Through their activities metabolic products, which are constantly formed in the body, usually do not have a significant impact on the osmotic pressure. Unlike the osmotic pressure of blood osmotic pressure, urine and sweat varies in rather wide limits. Depression sweat equal 0.18-0,60 degrees urine - 0,2-2,2 degrees. Particularly significant shifts of osmotic pressure of blood raises intense muscular work.