Platelet (Thrombocyte)

A **platelet** is not a cell but rather a fragment of the cytoplasm from a cell called megakaryocyte that is surrounded by a plasma membrane. Platelets are small, measuring 2–4 µm in diameter, but abundant, typically numbering between 150,000‒160,000 per µL of blood. Upon entering the bloodstream, about one-third of platelets migrate to the spleen for storage, where they remain available for release in response to vessel injury. When activated, platelets perform their primary function in limiting blood loss. With a lifespan of approximately 10 days, platelets are eventually removed by macrophages through phagocytosis. Platelets are essential to hemostasis, the process of stopping blood flow after vessel damage. They also secrete various growth factors important for tissue growth and repair, particularly in connective tissues. Concentrated platelet infusions are now used therapeutically in some treatments to stimulate healing. *LICENSES AND ATTRIBUTIONS CC licensed content, Shared previously, 2.4 Leukocytes and Platelets, Authored by: OpenStax College. License: CC BY: Attribution. License Terms: Download for free at:http://cnx.org/contents/0QN1UvTH@2.3:3xCcgfIV@5/Leukocytes-and-Platelets* ## Keywords platelet