Platelet are also called as thrombocytes. This blood cells are important in preventing bleeding after any injury and blood vessels damaged. This cells accumulate over the injured sites and form a plug that prevent excesive bleeding.
What are Platelets?
Platelets are structurally in small size compared to red blood cell and white blood cell. They are of disc shaped produced in the bone marrow. They emerge from a large cells called megakaryocytes.
Structure of Platelet
Platelets are small colorless cells, they dont have nucleus. It has granules in it filled with the proteins, enzymes and clotting factors that helps in blood clotting process.
Platelets are disc shaped in normal cases, during their actions they transform into the irregular, finger like projections to properly form plug and interlock with one another. Size of platelet is of 2 to 3micrometers in diameter.
Cell membrne of platelets is filled with glycoproteins, that act as a glue and helps in the process of sticking at injured blood vessel walls. It has cytoskeleton structure made with the actin and tubulin proteins, this helps them to adjust their shape whenever needed. At last, granules are there, they store chemicals like serotonin, calcium, ADP and clotting factors that helps in blood clotting process.
How does platelets forms?
Platelets are form in the bone marrow through a process called thrombopoiesis. Hematopoietic cells form the megakaryocyte cells. When the body needs the platelet, thrombopoietin (TPO) hormone is released by the liver and kidney. This hormone regulate platelet production. It signals the megarkaryocytes to matured. Later it breaks down into small fragments that ultimately becomes platelets entering the blood.
Normal Platelet Count
A normal platelet count is 150,000 to 450,000 platelets per microliter of blood in an adult. Low platelet count is called as thrombocytopenia and high platelet count is called thrombocytosis of the above normal count.
Functions of Platelets
The primary function of the platelets is to stop the bleeding from a broken blood vessels. It also supports healing through this process. Platelets perform this in three stages,
Stage 1 – In this the platelets accumulates at the injured site and stick to the collagen fibers of damaged blood vessels.
Stage 2 – In second stage, platelets changes their shape and released granules. This released chemicals further signal more platelets to come to the injury site.
Stage 3 – It is characterized by formation of plug. Platelets stick with each other and form a plug over injured site. Now the platelet plug is not so strong and act as a temporary patch.
So, platelets starts the coagulation cascade process with blood protiens. The presence of prothrombin is converts to thrombin. This thrombin then converts fibrinogen into strong strends of fibrin. This fibrin act as like a net which prevents blood loss. Later the RBC and WBC also get trapped into it to become a solid blood clot.