Transcript Platelets
MLAB1415- Hematology
Keri Brophy-Martinez
Platelets
Platelets
Production
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Bone marrow
Differentiation
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Comes from the CFU-GEMM
Platelets
Regulation
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TPO= thrombopoietin
Influences all stages of megakaryocyte production
Made in liver, kidney, spleen, and smooth muscle cells
Binds receptors in peripheral blood
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Bound TPO does not stimulate bone marrow progenitor
cells
– For example: Increased platelet count, more TPO is
bound, stimulation of bone marrow is decreased
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
Overview of Hemostasis
When vascular injury occurs, platelets do the following:
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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
Platelets: maturation sequence
Megakaryoblast
Size: 20-45µm
Cytoplasm
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Nucleus
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Blue, scanty, pseudopodia
No granules
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
Megakaryoblast
Promegakaryocyte
Size: 20-80µm
Cytoplasm:
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Basophilic
Few azurophilic granules
Nucleus
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Indented or bilobed
nucleus
Megakaryocyte
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Size: 30-100µm
Cytoplasm
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Nucleus
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Pinkish blue/abundant
Irregular border with occasional pseudopods
Abundant granules
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.
Megakaryocyte
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
Platelet (thrombocyte)
Platelets
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.