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MLAB1315- Hematology Keri Brophy-Martinez

MLAB1315- Hematology Keri Brophy-Martinez. Unit 4: Platelets. Platelets: maturation sequence. Production occurs in the bone marrow Megakaryoblast Size: 20-45µm Cytoplasm Blue, scanty, pseudopodia No granules Nucleus Single, round/oval, may be indented Central or eccentric

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MLAB1315- Hematology Keri Brophy-Martinez

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  1. MLAB1315- HematologyKeri Brophy-Martinez Unit 4: Platelets

  2. Platelets: maturation sequence • Production occurs in the bone marrow • 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

  3. Megakaryoblast

  4. Promegakaryocyte • Size: 20-80µm

  5. 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 1:12 • Membrane ruptures after maturation is complete, cytoplasm fragments resulting in 1000 to 2000 platelets. The nucleus is phagocytized.

  6. Megakaryocyte

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

  8. Platelet (thrombocyte)

  9. Function of platelets • Normally circulate in a discoid shape • Help to maintain hemostasis and capillary integrity (this will be discussed in detail in Coagulation) • 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 • Platelets contain the following storage granules that are released when the platelets adhere to the vessel surface: • Alpha • Dense • Delta

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