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MLAB1415- Hematology Keri Brophy-Martinez

MLAB1415- Hematology Keri Brophy-Martinez. Platelets. Platelets. Production Bone marrow Differentiation Comes from the CFU-GEMM. Platelets. Regulation TPO= thrombopoietin Influences all stages of megakaryocyte production Made in liver, kidney and spleen

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MLAB1415- Hematology Keri Brophy-Martinez

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  1. MLAB1415- HematologyKeri Brophy-Martinez Platelets

  2. Platelets • Production • Bone marrow • Differentiation • Comes from the CFU-GEMM

  3. Platelets • Regulation • TPO= thrombopoietin • Influences all stages of megakaryocyte production • Made in liver, kidney and spleen • Binds receptors in peripheral blood • Bound TPO does not stimulate bone marrow progenitor cells • For example: Increased platelet count, more TPO is bound, stimulation of bone marrow is decreased

  4. Function of platelets • Normally circulate in a discoid shape • Help to maintain hemostasis and capillary integrity (this will be discussed in detail in Coagulation) • Platelet to platelet interactions • Platelet to coagulation protein interactions • Aid in healing injured tissue

  5. Overview of Hemostasis • When vascular injury occurs, platelets do the following: • Adhere to the injured vessel • Aggregateand transform into reactive spiny spheres that interact with one another and form into a platelet plug • Consolidatewith fibrin into a clot • Stabilizewith the aid of a coagulation factor

  6. Platelets: maturation sequence • Megakaryoblast • Size: 20-45µm • Cytoplasm • Blue, scanty, pseudopodia • No granules • Nucleus • Single, round/oval, may be indented • Central or eccentric • Red purple with fine and distinct chromatin • 1-2 nucleoli • Nucleus divides by endoreplication meaning the nuclear material reduplicates, but the nucleus does not divide resulting in a multilobed nucleus and abundant cytoplasm. • N:C ratio = 4:1

  7. Megakaryoblast

  8. Promegakaryocyte • Size: 20-80µm • Cytoplasm: • Basophilic • Few azurophilic granules • Nucleus • Indented or bilobed nucleus

  9. Megakaryocyte • Size: 30-100µm • Cytoplasm • Pinkish blue/abundant • Irregular border with occasional pseudopods • Abundant granules • Nucleus • Lobulated • Purple with granular chromatin • No nucleoli • N:C ratio = 1:1 to 1:2 • Membrane ruptures after maturation is complete, cytoplasm fragments resulting in 1000 to 2000 platelets. The nucleus is phagocytized.

  10. Megakaryocyte

  11. Platelet (thrombocyte) • Size: 1-4µm • Cytoplasm • Light blue (actually fragments of megakaryoctye cytoplasm) • Fine scattered granules • Nucleus not present • Reference range: 150,000 - 450,000/µl • Lifespan is 8-10 days

  12. Platelet (thrombocyte) Platelets

  13. References • Harmening, D. M. (2009). Clinical Hematology and Fundamentals of Hemostasis. Philadelphia: F.A Davis. • McKenzie, S. B., & Williams, J. L. (2010). Clinical Laboratory Hematology . Upper Saddle River: Pearson Education, Inc.

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