Which of the following is the final normal maturation stage for platelets?

• A. Megakaryoblast
• B. Promegakaryocyte
• C. Thrombocyte
• D. Megakaryocyte

Answer: (C)

Understanding how platelets mature helps you see why the final stage is thrombocyte. Platelets come from megakaryocytes in the bone marrow. The development sequence starts with a megakaryoblast, then progresses to a promegakaryocyte, and finally to a megakaryocyte. The megakaryocyte grows large and extends cytoplasmic processes; these processes fragment to release small, anucleate platelet pieces into the bloodstream. Those circulating platelets are called thrombocytes. So the last normal maturation stage for platelets is thrombocyte, because it represents the fully formed, functional platelet fragment ready to participate in hemostasis. The earlier terms—megakaryoblast, promegakaryocyte, and megakaryocyte—are precursor stages preceding platelet formation.