Questions and Answers
What is hematopoiesis?
The process of blood cell production in the blood forming organs.
Which of the following stages occur during prenatal hematopoiesis? (Select all that apply)
Hematopoiesis is a continuous and regulated process.
True
What does HSC stand for?
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The primary site of hematopoiesis during adult life is the _____
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What is the normal lifespan of a red blood cell (RBC)?
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What are the components of red marrow?
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Endomitosis results in an increase in the number of cells.
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Which type of cells are primarily produced in the fetal liver during prenatal hematopoiesis?
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Match the type of blood cell production with its corresponding term:
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What is the main reason for the decreased hemoglobin in metarubricytes?
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Which of the following are physiologic compartments of developing leukocytes? (Select all that apply)
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What is the earliest recognizable cell in the granulocytic series?
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What is the size range of a myeloblast?
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The N/C ratio of a myeloblast is ___.
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Which cell stage is known as the last stage capable of mitosis?
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What are the two types of granules that can be found in a promyelocyte?
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Monoblasts are the earliest recognizable cells in the monocytic series.
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What is the largest cell in the blood?
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Which cell is known to be the largest cell in the bone marrow?
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The CFU-GM cell is a multipotent progenitor.
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What is the primary function of macrophages?
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Study Notes
Hematopoiesis
- Blood cell production occurs in blood-forming organs, involving proliferation, differentiation, morphogenesis, functional maturation, and death.
- Hematopoietic stem cells (HSC) are responsible for self-renewal and differentiation into all blood cell lineages.
Cellular Proliferation
- Mitosis: nuclear division occurs across all blood lineages.
- Endomitosis: specific to megakaryocytes, resulting in increased cell size without cell number increment.
Morphogenesis and Functional Maturation
- Morphogenesis involves structural changes, such as granule production.
- Functional maturation includes hemoglobinization in red blood cells (RBCs), where nuclei are excluded leading to fully functional cells.
Types of Hematopoiesis
- Erythropoiesis: production of red blood cells.
- Leukopoiesis: production of white blood cells.
- Granulopoiesis: production of granulocytes.
- Lymphopoiesis: production of lymphocytes.
- Megakaryopoiesis: production of platelets.
- Monocytopoiesis: production of monocytes.
Prenatal Hematopoiesis
- Mesoblastic Stage: Begins around the 14th day of gestation; peaks from 1st to 3rd month in mesenchyme and erythroblastic islands of yolk sac.
- Hepatic Stage: Fetal liver becomes the main hematopoietic organ after the 3rd month; spleen, kidney, and thymus assist in hematopoiesis.
- Medullary Stage: Starts in the 4th month, with bone marrow becoming the primary site for hematopoiesis by 5th-6th month.
Hematopoiesis in Adulthood
- Red marrow is confined to axial skeleton and proximal ends of long bones post 18 years, while yellow marrow becomes prevalent.
- Extramedullary hematopoiesis may occur in response to certain conditions, with organs like the spleen and liver reverting to blood cell production.
Stem Cells and Progenitors
- HSCs are primitive cells that give rise to multipotent progenitors with the ability to become various blood cell types.
- Committed precursor cells progressively differentiate into specific blood lineages.
Characteristics of Blasts
- Blasts are large cells with high nuclear-cytoplasmic ratios and basophilic cytoplasm, indicating active RNA content.
- Lack of granules in the early stages, but specific granule presence develops as cells mature.
Erythrocytic Series
- Erythrokinetics covers the production, maturation, and destruction cycles of RBCs, emphasizing the connection between macrophages and senescent RBC removal.
- Key cell types: BFU-E (youngest), CFU-E (requiring EPO), Rubriblast (first recognizable), Metarubricyte (last nucleated stage), Reticulocyte (young RBC), and Mature erythrocyte (lifespan of 120 days).
Granulocytic Series
- Comprised various stages from myeloblast through mature granulocytes such as neutrophils, eosinophils, and basophils, each identifiable by size, nucleus form, and granule composition.
- Key granulopoietic cells: CFU-GM (multipotent progenitor), myeloblast (earliest recognizable), and granulocyte classifications by morphological characteristics.
Monocytic Series
- Monoblasts emerge from CFU-GM multipotent progenitors, challenging to distinguish from early myeloblasts.
General Functional Characteristics
- The development of blood cells is regulated by growth factors and the microenvironment, ensuring proper differentiation and maturation into functional blood cell types.### Differentiation Tests
- Morphologic criterion includes peroxidase, specific esterase, and Sudan staining.
- Monocytes show negative results for morphology tests while myeloblasts show positive results.
Cell Types and Characteristics
- Monoblast*
- Size: 12-20 µm.
- N/C ratio: 4-3:1.
- Nucleus: Ovoid or round, light blue-purple, fine lacey chromatin, 1-2 nucleoli.
- Cytoplasm: Moderately basophilic to blue-gray, non-granular.
- Promonocyte*
- Earliest morphologically recognizable cell.
- Size: 12-20 µm.
- N/C ratio: 3-2:1.
- Nucleus: Oval with potential single fold, fine chromatin, 1-5 nucleoli.
- Cytoplasm: Blue-gray, may have dust-like azurophilic granules and variable vacuoles.
- Monocyte*
- Largest cell in the blood.
- Low circulating count as they migrate and differentiate into macrophages.
- Size: 12-18 µm.
- N/C ratio: 2-1:1.
- Nucleus: Round, kidney-shaped, slight lobulation, linear chromatin without visible nucleoli.
- Cytoplasm: Abundant, blue-gray, azurophilic granules present, forms pseudopods and vacuoles.
- Macrophage*
- Exists as either fixed or wandering cells.
- Fixed examples include Kupffer cells (liver), Langerhans cells, microglia, and alveolar macrophages.
- Wandering macrophages can circulate in blood.
- Functions to phagocytose organisms or senescent cells.
- Size: 18-50 µm.
- N/C ratio: 1:2-4.
- Nucleus: Eccentric, egg yolk shaped, spongy chromatin pattern.
- Cytoplasm: Coarse azure granules, vacuolated with ingested materials, royal blue in color.
Lymphocytic Series
- Primary Lymphoid Organs*
- Bone marrow and thymus.
- Continuous antigen-independent lymphopoiesis occurs here to replenish cell loss.
- Secondary Lymphoid Organs*
- Include lymph nodes, spleen, tonsils, Peyer's patches, and lymphatic aggregates.
- Antigen-dependent; involved in lymphopoiesis during foreign body invasions.
- Lymphoid Progenitor*
- Differentiates into various lymphocyte types.
- Lymphoblast*
- Size: 10-18 µm.
- N/C ratio: 4:1.
- Nucleus: Round or oval with coarse chromatin, 1-2 nucleoli, no clumping.
- Cytoplasm: Smooth, no granules, ranging from moderate to dark blue.
- Prolymphocyte*
- Size: 10-18 µm.
- N/C ratio: 4:1.
- Nucleus: Round, oval, or slightly indented; clumped chromatin; may have 1-2 nucleoli.
- Cytoplasm: Moderate to dark-blue, predominantly nongranular but may contain azurophilic granules.
- Lymphocyte*
- Size: 8-16 µm.
- N/C ratio: 4-2:1.
- Nucleus: Round or oval, slight indentation, densely clumped chromatin, no nucleoli.
- Cytoplasm: Pale to dark-blue; may have few azurophilic granules.
Antigen-dependent Maturation Series
- Mature B-cell*
- Involved in antibody production.
- Plasmablast*
- Size: 18-25 µm.
- N/C ratio: 2:1.
- Nucleus: Eccentric with more clumped chromatin; multiple visible nucleoli.
- Cytoplasm: Abundant, basophilic, nongranular.
- Proplasmacyte*
- Size: 15-25 µm.
- N/C ratio: 1:1.
- Nucleus: Eccentric with coarser, densely stained chromatin.
- Cytoplasm: Abundant, intensely basophilic, often presents a hof or perinuclear area.
- Plasma Cell*
- Size: 8-20 µm.
- N/C ratio: 1:1.
- Nucleus: Eccentric with condensed chromatin, no visible nucleoli.
- Cytoplasm: Deeply basophilic with a well-defined hof next to the nucleus, rich in rough ER.
Megakaryocytic Series
- CFU-Meg*
- Committed progenitor for megakaryocytes.
- Megakaryoblast*
- Size: 20-50 µm.
- N/C ratio: 10:1.
- Nucleus: Fine chromatin with multiple nucleoli.
- Cytoplasm: Small to moderate, darker blue than myeloblast, nongranular.
- Promegakaryocyte*
- Size: 20-50 µm.
- N/C ratio: 4-7:1.
- Nucleus: Irregularly shaped with coarse chromatin, multiple nucleoli.
- Cytoplasm: Abundant, less basophilic, granules forming, Demarcation Membrane System developing.
- Granular Megakaryocyte*
- Size: 30-90 µm.
- N/C ratio: 1-2:1.
- Nucleus: Multiple or multilobulated, coarser chromatin.
- Cytoplasm: Abundant, pinkish-blue, diffusely granular, irregular border.
- Mature Megakaryocyte/Metamegakaryocyte*
- Size: 40-120 µm.
- N/C ratio: 1:1.
- Nucleus: Multiple or multilobulated with no visible nucleoli.
- Cytoplasm: Contains coarse granular clumps that bud off to form 2000-4000 platelets.
Thrombocytes
- Size: 1-4 µm.
- Composed of cytoplasmic fragments.
- Cytoplasm: Light blue to purple, very granular with an outer hyalomere and inner chromomere.
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Description
This quiz explores the intricate process of hematopoiesis, focusing on blood cell production, including proliferation, differentiation, and maturation. It highlights the role of hematopoietic stem cells in maintaining the blood cell lineages. Test your understanding of these crucial biological processes!
