An important condition for the correct functioning of the clotting system is the presence in the bloodstream of a certain number of mature platelets. Deviations in any direction can have adverse consequences. The norm of platelets in the blood differs according to age and sex. If their level is lowered, a tendency to bleeding appears, blood coagulability deteriorates, it is difficult to stop. If the content of platelets exceeds the norm, the blood becomes thick, there is a risk of blood clots and clogging of blood vessels.
Platelets are formed in the bone marrow from giant cells - megakaryocytes. In fact, they are fragments of these cells and are small, non-nuclear, colorless oval or round plates surrounded by a membrane, including granules. Diameter of platelets is from 2 to 4 microns. They are called blood cells, like leukocytes and erythrocytes, although they are not. These are postcell structures, or plaques of Bizzazero( named after the Italian scientist, who made a great contribution to their study).In blood there are about 2/3 of all platelets, the rest are contained in the spleen.
Functions of blood plates
If the vascular wall is damaged, the blood platelets activate immediately. They acquire a spherical shape, they appear outgrowths, because of what they become like a star. Platelets in the active form are capable of adhering to each other( aggregation) and adherence to the wall of the vessel( adhesion).In the blood plasma, they secrete an enzyme, under the action of which soluble fibrinogen is converted into insoluble fibrin, which entangles the uniform elements of the blood with its strands, like nets. The formed thrombus closes the defect in the damaged vessel. Platelets take part in dissolving the fibrin clot and maintain a spasm of damaged vessels. Another important function is the provision of nutrients to cells that lining the inner surface of blood vessels.
The determination of platelet count is included in the clinical blood test. This study allows physicians to evaluate the work of the clotting system, the ability of the body to cope with bleeding, and thus avoid death from hemorrhage. If the platelets are normal - this indicates a good hematopoiesis. The norm of platelets in men, women and children is not the same. In adults, their level should be:
- for women - 150-400H109 per liter of blood;
- for pregnant women - 100-420Х109;
- for men - 180-320H109.
The number of blood platelets in the blood can vary for some physiological reasons, but this is not a deviation from the norm. During the day, these fluctuations can be up to 10%.This can occur in the following cases:
- during pregnancy( may decrease by 25-50% due to an increase in the total volume of blood, which leads to a decrease in the concentration of the formed elements);
- during menstruation and within a week after their termination( these days, the platelet count can be significantly reduced( up to 75-220X109 depending on how profuse the monthly),
- with considerable physical exertion,
- with a shortage of vitamin B12 and folic acid in the dietacid
In children under the age of the year, the hematopoietic system is unstable, the differences in the values are not considered a deviation. The norm of platelets for children depends on age:
- in newborns is 100-420H10⁹ / liter,
- at the age of two weeks is 150-400H10⁹;from two weeks up to a year - 160-390Х10⁹;
- starting from one year and up to 5 years - 150-400Х10⁹;
- from 5 to 10 years - 180-450Х10⁹;
- from 10 to 15years - 150-450Х10⁹,
- from 15 to 18 years - 180-420Х10⁹
Read more about the norms in children and the reasons for the increase in platelets
Platelets take part in the formation of thrombus and stop bleeding
In the blooda person circulating platelets of five forms. Their level is as follows:
- 0.8% - young;
- 90-95% - mature;
- 2.2 - 5.6% - old;
- 0,8-2,3% - forms of irritation;
- 0,2% - degenerative.
How is the analysis done?
The platelet count is determined during a general blood test at the same time as counting other blood counts. Blood is taken from the finger in the morning hours - up to 10-11 hours. Before the procedure, one should not eat and drink sweet drinks - only pure water. For three hours before the analysis, smoking is not allowed. It is not recommended to drink alcoholic beverages the day before. The doctor should be warned about the passage of physiotherapy and taking medications.
Important! During the clinical analysis, only the total number of platelets is determined, but not the percentage of different forms. You should be aware that the absolute value may correspond to the norm, while the level of mature forms is lowered, and the level of the young and degenerate exceeds the permissible limits. In this case, the effectiveness of platelets is significantly reduced. To assess their activities, it is required to investigate their morphology, that is, the size, structure, form. The most complete picture of the state of the hemostasis system can be obtained with the help of a conventional or expanded coagulogram.
Platelets normally have a certain shape and size. With diseases in the blood, small or large caudate forms are found, their internal structure and color changes. Using a microscope, they study their functionality, that is, the ability to aggregate and adhere. To evaluate the activity, the blood obtained from the vein is better suited. The study of functional consistency is of great importance in the diagnosis of certain pathologies, such as von Willebrand disease, congenital thrombocytopenia, Bernard-Soulier disease and others.
How is the platelet count calculated?
The number of blood plates is determined by different methods: using smears( Fonio) and chamber( in the chamber Goryaev).Recently, automatic counters of blood elements have been increasingly used. It is particularly convenient to use the Fonio method with this form of counting. Reagents are required for this procedure:
- 14% magnesium sulfate( sterile solution);
- Leishman retainer or Main-Grunwald retainer;
- dye Romanovskogo - Giemsa.
To calculate the number of platelets by the Fonio method, the finger is processed, then it is wiped dry and punctured. Then, magnesium sulphate( 1 drop) is dripped onto the finger and mixed with the blood that has escaped from the puncture. From the resulting mixture make smears, which are dried and stained.
The determination of the number of blood cells is carried out using automatic counters
. In a colored smear, 1000 red cells are counted and all the platelets that fall during this time. Get a relative amount, which is measured in ppm. To learn the absolute level of blood platelets, the resulting value is multiplied by the number of red blood cells contained in 1 μl of blood, then divided by 1000.
What is the danger of abnormality?
If the content of the blood platelets does not correspond to the norm, there is a threat of the development of pathological conditions that can turn into a fatal outcome. Violation of blood coagulability leads to severe consequences, in which mortality is high enough. Among them:
- life-threatening profuse bleeding with poor coagulation;
- thromboses, strokes and heart attacks with increased coagulability.
Indications for platelet analysis
Analysis is relevant for suspected coagulation disorders. Suspicion of a decrease in the level of platelets can be on the following grounds:
- long and profuse menstruation;
- often comes from the nose;
- gum bleeding;
- for scratches, cuts and other minor damages the blood does not stop for a long time;
- bruises are formed even with minor effects;
- point rashes on the skin.
It is important to monitor the level of platelets during the gestation of the fetus. This is due to the fact that during pregnancy, changes in the blood coagulation system can occur.
Platelets perform a vital function in the body - take a direct part in blood clotting and the process of repairing the damaged vessel. Thus, they protect a person from death as a result of blood loss. A significant deviation from the normal level in either direction may indicate a pathology. A more dangerous sign is the decrease in platelet count. If it drops below 150X109( excluding the period of pregnancy and menstruation in women) and remains stably low for a long time, it is necessary to find out the causes of thrombocytopenia and start treatment on time. The increase in the level of blood platelets( thrombocytosis) occurs less often, but it can not be ignored, since this condition can also indicate severe illnesses.