At platelets they are blood structures which, unlike the Red Cells and leukocytes, are not cells, but cytoplasmic fragments. On average, a normal adult individual has 125,000 to 450,000 platelets per mm3, and about 30,000 are formed daily.
→ General characteristics of platelets
Platelets are cytoplasmic fragments of megakaryocytes produced in the bone marrow. As they are fragments, these cells do not have a nucleus, therefore, anucleate. They have a discoid shape about 2-4 μm in diameter and a very complex internal structure divided into four zones: peripheral zone, sol-gel zone, organelle zone and membrane system.
The inside of the platelet is able to communicate with the external environment due to the presence of a channel system known as open canalicular system. This communication is important, as it guarantees the release of molecules stored in platelets.
Platelets have a very short circulation time in the blood, taking, on average, 10 days to be removed. These cell fragments are removed from the circulation by the reticuloendothelial cells of the liver and spleen.
→ Platelet Functions
Platelets have important functions for the maintenance of our body. When, for example, there is an injury to a blood vessel, they agglutinate, forming a plug, and release substances that ensure that more platelets move to the site. In addition, they participate in the coagulation cascade, releasing important substances that ensure the formation of a clot. It is worth noting that platelets also have enzymes that contribute to clot removal.
→ Platelet-related abnormalities
Plateletopenia: It occurs when the patient has a reasonable drop in the normal number of platelets. This analysis can be done after counting platelets in a blood sample. When a patient has thrombocytopenia, bleeding occurs more easily, as well as the appearance of bruises throughout the body. The patient may also have bloody stools, vomiting blood, joint and muscle pain, and weakness.
Plateletosis: It occurs when a patient has a high number of platelets in the blood. It can be classified, analyzing the increase in platelets, in mild, moderate, severe and extreme. In the latter case, the number is greater than 1,000,000 platelets per mm3. Thrombocytosis can be further classified into primary and secondary. The primary is related to myeloproliferative diseases (related to the abnormal production of blood cells), and the secondary is triggered by some underlying disease, such as infections and anemias.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-sao-plaquetas.htm