Download - MLAB1415- Hematology Keri Brophy-Martinez
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MLAB1415- Hematology
Keri Brophy-Martinez
Platelets
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Platelets
Production– Bone marrow
Differentiation– Comes from the CFU-GEMM
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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
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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
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Overview of Hemostasis
When vascular injury occurs, platelets do the following:– Adhere to the injured vessel– Aggregate and transform into reactive spiny spheres that
interact with one another and form into a platelet plug– Consolidate with fibrin into a clot
– Stabilize with the aid of a coagulation factor
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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
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Megakaryoblast
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Promegakaryocyte
Size: 20-80µm Cytoplasm:
– Basophilic– Few azurophilic granules
Nucleus– Indented or bilobed
nucleus
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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.
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Megakaryocyte
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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
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Platelet (thrombocyte)
Platelets
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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.