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Questions and Answers
What is the normal reference value (N.V.) for platelet count?
What is the normal reference value (N.V.) for platelet count?
Which sex tends to have a higher platelet count?
Which sex tends to have a higher platelet count?
What percentage of platelets are found circulating in the blood?
What percentage of platelets are found circulating in the blood?
What initiates primary hemostasis?
What initiates primary hemostasis?
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What is the end product of primary hemostasis?
What is the end product of primary hemostasis?
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Where are approximately 30% of platelets typically stored?
Where are approximately 30% of platelets typically stored?
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What happens to the primary hemostasis process after a brief period?
What happens to the primary hemostasis process after a brief period?
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What role do proplatelet processes play in platelet formation?
What role do proplatelet processes play in platelet formation?
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Which hormone is essential for the early stages of megakaryocytopoiesis?
Which hormone is essential for the early stages of megakaryocytopoiesis?
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Which cell type undergoes endomitosis leading to less proliferation?
Which cell type undergoes endomitosis leading to less proliferation?
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Where is the primary production of Thrombopoietin (TPO) located?
Where is the primary production of Thrombopoietin (TPO) located?
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In the terminal differentiation stage, how can immature megakaryocytes be differentiated?
In the terminal differentiation stage, how can immature megakaryocytes be differentiated?
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Which interleukin is important in the later stages of megakaryocytopoiesis?
Which interleukin is important in the later stages of megakaryocytopoiesis?
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What is the characteristic of BFU-Meg among the other megakaryocyte progenitors?
What is the characteristic of BFU-Meg among the other megakaryocyte progenitors?
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What is the initial identifiable stage in the development of megakaryocytes?
What is the initial identifiable stage in the development of megakaryocytes?
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Which cytokine is not mentioned as involved in megakaryocytopoiesis?
Which cytokine is not mentioned as involved in megakaryocytopoiesis?
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What technique is used to identify megakaryocyte progenitors in the bone marrow?
What technique is used to identify megakaryocyte progenitors in the bone marrow?
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What is the role of thrombopoietin (TPO) in the bone marrow?
What is the role of thrombopoietin (TPO) in the bone marrow?
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Where in the body does megakaryocytopoiesis occur?
Where in the body does megakaryocytopoiesis occur?
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What is the size range of platelets (thrombocytes)?
What is the size range of platelets (thrombocytes)?
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Which of the following cells are the largest in the bone marrow?
Which of the following cells are the largest in the bone marrow?
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Which of the following best describes the cytoplasm of platelets?
Which of the following best describes the cytoplasm of platelets?
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What is endomitosis?
What is endomitosis?
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What is the function of flow cytometry in megakaryocyte production?
What is the function of flow cytometry in megakaryocyte production?
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What major component is absent in platelets that distinguishes them from other blood cells?
What major component is absent in platelets that distinguishes them from other blood cells?
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What does the 'LD' in LD-CFU-Meg stand for?
What does the 'LD' in LD-CFU-Meg stand for?
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What are the two parts of the platelet's cytoplasm?
What are the two parts of the platelet's cytoplasm?
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Which progenitor cell undergoes the first stage of endomitosis?
Which progenitor cell undergoes the first stage of endomitosis?
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Which system forms a series of channels that aid in thrombocyte production?
Which system forms a series of channels that aid in thrombocyte production?
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What happens to megakaryocyte nuclei during thrombopoiesis?
What happens to megakaryocyte nuclei during thrombopoiesis?
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Why are platelets considered small under the microscope?
Why are platelets considered small under the microscope?
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What characterizes the hyalomere component of the platelet's cytoplasm?
What characterizes the hyalomere component of the platelet's cytoplasm?
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What is the primary role of phospholipase A2 in platelets?
What is the primary role of phospholipase A2 in platelets?
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Which structure is responsible for maintaining the discoid shape of platelets?
Which structure is responsible for maintaining the discoid shape of platelets?
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What is the thickness range of the glycocalyx in platelets?
What is the thickness range of the glycocalyx in platelets?
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What is the primary function of the sol-gel zone in platelets?
What is the primary function of the sol-gel zone in platelets?
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Which component is NOT involved in platelet adhesion and aggregation?
Which component is NOT involved in platelet adhesion and aggregation?
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What happens to the cytoskeleton of platelets when they are refrigerated?
What happens to the cytoskeleton of platelets when they are refrigerated?
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What is the effect of warming refrigerated platelets to 37°C?
What is the effect of warming refrigerated platelets to 37°C?
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What is the primary role of the dense tubular system in platelets?
What is the primary role of the dense tubular system in platelets?
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What role does ADP play in platelet function?
What role does ADP play in platelet function?
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Which of the following best describes the process of platelet adhesion?
Which of the following best describes the process of platelet adhesion?
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What is the function of lysosomes in platelets?
What is the function of lysosomes in platelets?
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What occurs after platelet activation?
What occurs after platelet activation?
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Which molecule is specifically mentioned as having an unknown function upon platelet activation?
Which molecule is specifically mentioned as having an unknown function upon platelet activation?
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What sequence correctly represents the formation of a platelet plug?
What sequence correctly represents the formation of a platelet plug?
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Which of the following components is a vasoconstrictor released by platelets?
Which of the following components is a vasoconstrictor released by platelets?
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Which ions are mentioned as supporting platelet activation and coagulation?
Which ions are mentioned as supporting platelet activation and coagulation?
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Study Notes
Hematopoiesis: Platelet Production
- Megakaryocytopoiesis is the production and development of megakaryocytes
- Progenitor cell: Common myeloid progenitor (CMP) or CFU-GEMM
- Lineage: Megakaryocyte-Erythrocyte Progenitor
- Site: Bone marrow (specifically red bone marrow)
- Megakaryoblasts develop into megakaryocytes, which produce platelets (thrombocytes)
- Megakaryocytes are the largest cells in bone marrow, containing multiple chromosome copies (polyploid)
- Thrombopoietin (TPO) is a liver-produced hormone that triggers megakaryocytopoiesis
Stages of Megakaryocyte Development
- Megakaryoblast: First identifiable stage
- Promegakaryocyte
- Megakaryocyte
- Platelets
Hematopoietic Stem Cells (CD34)
- Pluripotential hematopoietic stem cell
- Multipotential stem cells
- Committed progenitor cells
- CFUs (CFU-GM, CFU-Eo, CFU-Baso, CFU-MegE, CFU-G, CFU-M, BFU-E, CFU-Meg, LD-CFU-Meg): various committed progenitor cells like granulocytes, monocytes, eosinophils, basophils, megakaryocytes, erythrocytes, and precursors of T cells, NK cells and B cells
Endomitosis
- A type of cell division unique to megakaryocytes
- DNA replicates, but cytokinesis (division of cytoplasm) does not occur
- Allows megakaryocytes to develop multiple copies of their genome
- Low-density CFU-megakaryocytes (LD-CFU-Meg) undergo endomitosis
- Megakaryocytes lose the ability to divide after endomitosis
Hormones and Cytokines for Megakaryopoiesis
- Thrombopoietin (TPO): Primarily produced by the liver; induces stem cell differentiation, proliferation, and platelet release
- Interleukins (IL-3, IL-6, IL-11): Support megakaryocyte maturation and platelet release
- Stem cell factor (SCF): Supports megakaryocytic progenitor proliferation.
- Granulocyte-macrophage colony-stimulating factor (GM-CSF): Supports megakaryocytic progenitor proliferation.
- Granulocyte-CSF (G-CSF) : Supports megakaryocytic progenitor proliferation
Platelets (Thrombocytes)
- Small, anucleate cell fragments
- Cytoplasm contains granules (alpha granules, dense granules) and a cytoskeleton
- Primary role in hemostasis; forms the initial plug to stop bleeding
- Circulate in blood; lifespan of about 8-12 days
- Destroyed by macrophages in the spleen and liver
Platelet Structure and Function
- Peripheral Zone: Glycocalyx (outer surface), plasma membrane (phospholipids and carbohydrates), cytosol.
- Sol-Gel Zone: Cytoskeleton (microfilaments, microtubules) that supports and maintains platelet shape
- Organelle Zone: Alpha granules (contain proteins involved in clotting cascade, e.g., VWF, fibrinogen, etc.), dense granules (contain ADP, ATP, serotonin, calcium), mitochondria
- Membranous System: Dense tubular system, open canalicular system.
Stress Platelets (Reticulated Platelets)
- Platelets that are produced more rapidly in response to decreased platelet numbers, or inflammation.
- They are larger than mature platelets.
Platelet Plug Formation
- Platelets adhere to exposed collagen (and VWF(von Willebrand factor) at an injury site.
- Platelets release granules containing clotting factors.
- Platelets aggregate (clump together) to form a plug and trigger secondary hemostasis
- Platelets activate via shape change (change from disc to irregular).
- Platelet aggregation occurs once platelets are activated
Platelet Ultrastructure
- Primarily consists of protein, phospholipids, carbohydrates, electrolytes, and water.
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Description
This quiz covers the process of hematopoiesis with a focus on megakaryocytopoiesis and platelet production. Learn about the lineage, stages of development, and the role of thrombopoietin in megakaryocyte formation. Test your knowledge on the key concepts and cell types involved.
