Platelets (synonym: blood platelets, plaques, Bizzozero) is formed blood elements.
platelets Platelets are formed from the cytoplasm of megakaryocytes, the bone marrow by adsorbance of its fragments. Platelets - nuclear free education are round or oval in shape, size 1 - 3 MK. At colouring Romanovsky - Giemsa in platelets can be distinguished centrally located granulomas with small red-violet grain and the surrounding pink-blue or non-grainy Galomar. In pathological conditions platelets become irregular shape and other, sometimes gigantic sizes. The normal number of platelets in the blood of 200 000 - 400 000 1 mm3. Leukocyte count - see the Blood.
Platelets plays an important role in stopping bleeding. If damaged capillaries platelets, agglutinins, close to the vessel lumen. In platelets, see "laminar"factors involved in all phases of blood clotting. So transfusion trombotsitnoy estate used to stop bleeding. The increase in the number of platelets - thrombocytosis - bears the risk of thrombosis. He observed after bleeding, operations, especially after splenectomy (see), hemolytic crises, myelogenous leukemia, erythremia, infectious diseases. The decrease in the number of platelets - thrombocytopenia (see).

Blood platelets, platelets or plaques are plasmatic education oval or round shape, the diameter of 2-5 MK. In humans and the mammals they have no nuclei, so most researchers believe it platelets non-cellular structures. The absence of nuclei distinguishes blood platelets from platelet - typical nuclear cells present in the blood of lower vertebrates.
The number of blood platelets in the blood is 200 000-400 000 1 mm3, but it can vary considerably. There are daily fluctuations in the number of blood platelets in the peripheral blood of their day more and less at night. Perhaps it depends on the rhythm of work and rest; after heavy physical exertion, the number of blood platelets in humans increases in 3-5 times. Duration of blood platelets is 2-5 days, so all is contained in blood, their number is renewed every 2-5 days. Platelets are formed by megakaryocytes - giant cells found in the red bone marrow and spleen.
Platelets are quickly dissolved in the blood, released from the blood vessel. Of blood platelets go to plasma factors that play a role in blood coagulation, and retraktsii.
In the decay of blood platelets from them, a vasoconstrictor substance - serotonin (5-gidroksietilimino). Thus, platelets prevent bleeding not only because it increases blood clotting, but that secrete a substance constricting the blood vessels. This is the protective role of blood platelets in the body.