In this article, we consider the properties of blood plasma. Blood is of great importance in the metabolic processes of the human body. It includes plasma and the shaped elements suspended in it: erythrocytes, platelets and white blood cells, which occupy about 40-45%, 55-60% of the elements that make up the plasma.
What is plasma?
Blood plasma is a liquid with the same viscous structure of light yellow color. If you consider it as a suspension, you can detect blood cells. Plasma is usually clear, but eating fatty foods can make it cloudy.
What are the main properties of plasma? About it further.
The composition of the plasma and the functions of its parts
Most of the plasma composition (92%) is occupied by water. In addition, it contains substances such as amino acids, glucose, proteins, enzymes, minerals, hormones, fat, as well as fat-like substances. The main protein is albumin. It has a low molecular weight and occupies more than 50% of the total protein volume.
The composition and properties of plasma are of interest to many medical students, and the following information will be useful to them.
Proteins take part in metabolism and synthesis, regulate oncotic pressure, are responsible for the preservation of amino acids, and carry various kinds of substances.
Also, large-molecular globulins, which are produced by the organs of the liver and the immune system, are isolated in the composition of the plasma. Alpha, beta and gamma globulins are distinguished.
Fibrinogen - a protein that is formed in the liver, has the property of solubility. Due to the influence of thrombin, it can lose this sign and become insoluble, as a result of which a blood clot appears where the vessel was damaged.
The blood plasma, in addition to the above, contains proteins: prothrombin, transferrin, haptoglobin, complement, thyroxin-binding globulin and C-reactive protein.
Blood plasma functions
It performs a lot of functions, among which stand out:
- transport - transfer of metabolic products and blood cells;
- the binding of liquid media located outside the circulatory system;
- contact - provides communication with tissues in the body using extravascular fluids, which allows the plasma to carry out self-regulation.
Physico-chemical properties of plasma
Blood plasma is rich in platelets. It is used in medicine as a stimulant for the regeneration and healing of body tissues. The proteins that make up the plasma provide blood coagulation, the transport of nutrients.
Also, thanks to them, the functioning of the acid-base hemostasis occurs, the state of aggregation of the blood is maintained. Albumin performs synthesis in the liver. Cells and tissues feed, bile substances are transported, as well as a reserve of amino acids. Let us single out the main chemical properties of plasma:
- Albumin delivered drug components.
- α-globulins activate protein production, transport hormones, trace elements, lipids.
- β-globulins transport cations of elements such as iron, zinc, phospholipids, steroid hormones and bile sterols.
- G-globulins contain antibodies.
- Blood coagulation depends on fibrinogen.
The most significant properties of blood of a physico-chemical nature, as well as its components (including plasma properties) are as follows:
- osmotic and oncotic pressure;
- suspension stability;
- colloidal stability;
- viscosity and specific gravity.
Osmotic pressure
Osmotic pressure is directly related to the concentration of dissolved substances in the plasma, the sum of the osmotic pressures of the various ingredients in its composition. This pressure is a rigid homeostatic constant, which in a healthy person is approximately 7.6 atm. It transfers the solvent from less concentrated to more saturated through a semi-impermeable membrane. It plays a significant role in the dispersal of water between cells and the internal environment of the body. We consider the main properties of plasma below.
Oncotic pressure
Oncotic pressure is the pressure of the osmotic type, which is created in a colloidal solution by proteins (another name is colloidal osmotic). Since plasma proteins have poor penetration into the tissue medium through the walls of capillaries, the oncotic pressure that they create holds water in the blood. In this case, the osmotic pressure is the same in tissue fluid and plasma, and the oncotic pressure is much higher in the blood. In addition, a reduced concentration of proteins in the tissue fluid is associated with the fact that they are washed out by the lymph from the extracellular medium; between tissue fluid and blood there is a difference in protein saturation and oncotic pressure. Since plasma contains the highest albumin content, oncotic pressure in it is created mainly by this type of protein. Reducing them in plasma leads to a loss of water, tissue edema, and an increase leads to a retention of water in the blood.
Suspension properties
The suspension properties of plasma are interrelated with the colloidal stability of the proteins in its composition, that is, with the preservation of cellular elements in suspension. The indicator of these blood properties is estimated by the erythrocyte sedimentation rate (ESR) in the immovable blood volume. The following ratio is observed: the more albumin is contained in comparison with less stable colloidal particles, the higher the suspension properties of blood. If the level of fibrinogen, globulins and other unstable proteins increases, ESR increases and the suspension capacity decreases.
Colloidal stability
Colloidal stability of the plasma is determined by the properties of hydration of protein molecules and the presence on their surface of a double layer of ions that create a phi potential (surface), which includes a zeta potential (electrokinetic) located at the junction between the colloidal particle and the liquid surrounding it. It makes it possible for particles to slip in a colloidal solution. The higher the zeta potential, the stronger the protein particles repel each other, and on this basis the stability of the colloidal solution is determined. Its value is much higher for albumin in the plasma, and its stability is most often determined by these proteins.
Viscosity
Blood viscosity is the ability to resist the flow of fluid during particle movement using internal friction. On the one hand, this is a complex relationship between colloid macromolecules and water, and on the other hand, between shaped elements and plasma. Plasma viscosity is higher than that of water. The more it contains large molecular weight proteins (lipoproteins, fibrinogen), the stronger the viscosity of the plasma. In general, this property of blood is reflected in the general peripheral vascular resistance to blood flow, that is, it determines the functioning of the heart and blood vessels.
Specific gravity
The specific gravity of the blood is associated with the number of red blood cells and the content of hemoglobin in them, the plasma structure. In a middle-aged adult, ranges from 1,052 to 1,064. Due to the different content of red blood cells in men, this figure is higher. In addition, the specific gravity increases due to fluid loss, excessive sweating during physical labor and high air temperature.
We examined the properties of plasma and blood.