Plasma contains low molecular crystalline substances (such as sodium hydroxide, sodium bicarbonate and glucose) and high molecular colloidal substances (such as protein).The osmotic pressure of plasma is the total osmotic pressure produced by these two substances.The osmotic pressure generated by low molecular crystal material is calledCrystal osmotic pressureThe osmotic pressure generated by polymer colloid material is called colloid osmotic pressure.
Chinese name
Colloid osmotic pressure
Foreign name
Colloid Osmotic Pressure
Definition
Terminology of physiology and cardiovascular medicine
Meaning
It plays an important role in maintaining the water balance inside and outside the blood vessels
The mass concentration of macromolecular colloidal substances in plasma is about 70 g/L, which is much higher than that of low molecular crystalline substances (7.5 g/L).The concentration of polymer colloid material is high, but the osmotic pressure generated by it is very low (about 3.85 kPa), which is due to therelative molecular massLarge, the number of particles in the unit volume of plasma is small.Although the content of low-molecular-weight crystal material is small, due to its small relative molecular weight, some can be ionized into ions, and there are many particles in the unit volume of plasma, the plasma osmotic pressure is mostly produced by low-molecular-weight crystal material (about 995%), colloid osmotic pressure only accounts for a small part.
Maintain balance
Announce
edit
Maintain relative balance of water inside and outside capillaries
Capillary wallDifferent from cell membrane, it is separated from plasma and intercellular fluid, allowing water molecules, ions and low molecular substances to pass through freely, but not allowing high molecular substances such as proteins to pass through.Therefore,Crystal osmotic pressureIt has no effect on maintaining the water salt balance between plasma and interstitial fluid.Under normal circumstances, the concentration of protein in plasma is higher than that in interstitial fluid, which can enable capillaries to "absorb" water from interstitial fluid (water penetrates from interstitial fluid to capillaries). At the same time, it can prevent water in blood vessels from excessively penetrating into interstitial fluid, thus maintaining the relative balance of water inside and outside blood vessels and maintaining blood volume.If for some reasonPlasma proteinDecrease,Plasma colloid osmotic pressureWhen the blood volume decreases, the water in the plasma will enter the interstitial fluid too much through the capillary wall, resulting in a decrease in blood volume and an increase in interstitial fluid, which is one of the reasons for edema.In clinical practice, patients with large area burns or excessive blood loss and reduced blood volume should be supplemented withnormal salineIn addition, plasma ordextranPlasma is replaced to restore plasma colloid osmotic pressure and increase blood volume.It can be seen that colloid osmotic pressure plays an important role in maintaining the relative balance of water inside and outside capillaries.[2]
