Platelets (synonym: blood plates, Bitstsotsero plaques) are the shaped elements of blood.
Platelets are formed from the cytoplasm of bone marrow megakaryocytes by detaching its fragments. Platelets - nuclear-free formations of a round or oval shape with a size of 1 - 3 microns. When stained according to Romanovsky – Giemsa in platelets, one can distinguish a centrally located granulometer with a fine red-violet grit and a pink-blue non-granular surrounding it. In pathological conditions, platelets acquire an irregular shape and other, sometimes gigantic, sizes. The normal number of platelets in the blood is 200,000–400,000 in 1 mm 3 . Platelet count - see Blood.
Platelets play an important role in stopping bleeding. If the capillaries are damaged, the platelets agglutinate to close the lumen of the vessel. Platelets contain “platelet factors” that take part in all phases of blood coagulation . Therefore, platelet transfusions are used to stop bleeding. An increase in the number of platelets - thrombocytosis - carries the risk of thrombosis. It is observed after bleeding, surgery, especially after splenectomy (see), with hemolytic crises, myeloid leukemia, erythremia, infectious diseases. Reducing the number of platelets - thrombocytopenia (see).Go
Blood plates, platelets or plaques, are plasma formations of oval or rounded shape, with a diameter of 2-5 microns. In humans and mammals, they do not have nuclei, so most researchers consider the blood platelets to be non-cellular formations. The absence of nuclei distinguishes blood plates from platelets - typical nuclear cells present in the blood of lower vertebrates.
The number of blood plates in human blood is 200 000–400 000 per 1 mm 3 , but it can vary considerably. There are daily fluctuations in the number of platelets: in the peripheral blood during the day there are more of them, and at night less. It is possible that it depends on the rhythm of work and rest; after heavy muscular work, the number of platelets in humans increases by 3-5 times. The duration of the existence of platelets is 2-5 days, so all their number in the blood is updated every 2-5 days. Blood plates are formed by megakaryocytes - giant cells located in the red bone marrow and spleen.
Blood plates are rapidly destroyed in the blood released from the blood vessel. Factors that play a role in blood coagulation come out of blood plates and retractozymes.
With the breakdown of blood platelets, vasoconstrictor is released from them - serotonin (5-hydroxytryptamine). Thus, the blood plates prevent bleeding, not only by increasing blood clotting, but also by releasing a substance that narrows the vessels. This is the protective role of blood platelets in the body.