Through the Microscope: Blood Cells - Life's Blood

Platelets

Platelets are the cytoplasmic fragments of megakaryocytes, circulating as small discs in the peripheral blood. They are responsible for hemostasis (the stoppage of bleeding) and maintaining the endothelial lining of the blood vessels. During hemostasis, platelets clump together and adhere to the injured vessel in this area to form a plug and further inhibit bleeding. Platelets average 1 to 4 µm in diameter. The cytoplasm stains light blue to purple, and is very granular. There is no nucleus present. Normal blood concentrations range from 130,000 to 450,000/µL.