Colorless nonnuclear disk‐shaped structure, 2–4 μm in diameter, found in the blood of all mammals. It is derived from fragments of megakaryocyte cytoplasm and released from the bone marrow into the blood. Contains active enzymes and mitochondria and has an important role in blood coagulation by adhering to other platelets and to damaged epithelium. Called also blood platelet, thrombocyte.
A round or oval disk, 2 to 4 μm in diameter, found in the blood of vertebrates. Platelets number 130,000 to 400,000/mm3. They are fragments of megakaryocytes, large cells found in the bone marrow.