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What are thrombocytes? How are they formed?

Last updated date: 20th Jun 2024
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Hint: These are the smallest blood cells and, because of their comparatively minute size, occupy a much smaller fraction of the volume of the blood. Within them, tiny granules contain substances that are essential for clot-promoting activity.

Complete answer:
> Platelets, also referred to as thrombocytes, are a blood component whose role (along with coagulation factors) is to respond by clumping to bleeding from blood vessel damage, thus inducing a blood clot. Biconvex discoid (lens-shaped) structures, 2-3 μm in maximum diameter, are circulating non-activated platelets. Enabled platelets have projections of a cell membrane covering their surface.

> There is no cell nucleus in platelets; they are cytoplasmic fragments that are produced from bone marrow megakaryocytes, which then enter the circulation. Platelets are present only in humans, while thrombocytes circulate as intact mononuclear cells in other vertebrates (e.g., birds, amphibians).

> Thrombopoietin, a hormone produced in the kidneys and liver, controls megakaryocyte and platelet production. During its life cycle, each megakaryocyte produces between 1,000 and 3,000 platelets.

> In a healthy adult, an average of 10$^{11}$ platelets are formed every day. Reserve platelets are stored in the spleen and are released by the sympathetic nervous system-induced splenic contraction when required. For circulating platelets, the average life period is 8 to 9 days. Old platelets in the spleen and liver are killed by phagocytosis.

> Because of platelet disorders, spontaneous and excessive bleeding may happen. Deficient numbers of platelets or dysfunctional platelets may cause this bleeding. Venous thrombosis and arterial thrombosis may result from excessive numbers of platelets, and/or normal platelets reacting to irregular vessel walls.

> NSAIDS (Non-steroidal anti-inflammatory drugs) are used to treat inflammation by blocking normal platelet function with an undesirable side effect.

Note: In innate immunity, platelets play a central function in activating and engaging in several inflammatory processes, directly binding and even killing pathogens. This confirms clinical evidence showing that many have thrombocytopenia with extreme bacterial or viral infections, thus decreasing their contribution to inflammation.