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HEMATOPOIESISJOSE R. VILLARINO, RMT

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Theories on Blood Cell Formation A. MONOPHYLETIC THEORY All blood cells come from one origin stem cell the HEMOCYTOBLAST REC B. POLYPHYLETIC THEORY Also known as Dualistic Theory which suggests different groups of blood cells originate from different stem cells.- RBC,WBC, platelets – Hemohistioblast- Monocytes, lymphocytes & plasma cells – Tissue hemohistioblast

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Stages of Hematopoiesis Mesoblastic stage – first month of embryonic life where cells are formed outside the embryo in the mesenchyme of the yolk sac. Hepatic stage – by the 6th week Medullary stage – by the 5th month blood cell formation occurs in the bone marrow. - Marrow – primitive stem cells & committed progenitor cells are confined - Spleen & lymph nodes – 2ndary lymphoid tissue for lymphocyte development and differentiation.

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Principles in Normal Cell Maturation CELL SIZE – immature cells are much bigger than more mature cells CYTOPLASMIC DIFFERENTIATION - amount of cytoplasm - color (basophilia) - presence of granules (WBC) NUCLEAR MATURATION - presence, size (nucleus:cytoplasm ratio) - nucleolus presence & lobes or indentation

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ERYTHROPOIESIS Governed by a hormone produced by the kidneys called ERYTHROPOIETIN Begins with the multipotential stem CFU-S. By the action of microenvironmental factors the CFU- S differentiates forming a committed erythroid progenitor cell.

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RBC Maturation Program Pronormoblast (Erythroblast) Basophilic normoblast (Prorubricyte) Polychromatic erythroblast (Rubricyte) Orthochromic normoblast (Metarubricyte) Reticulocyte (Polychromatophilic) Mature erythrocyte

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Pronormoblast (Rubriblast) First recognizable RBC precursor First Hemoglobin-synthesizing cell Approximately 20 um Moderate amount of cytoplasm Basophilic cytoplasm with 1-3 nuclei Prominent nuclear membrane Shows active mitotic division

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Pronormoblast (rubriblast)

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Basophilic normoblast(prorubricyte) Slightly smaller than the rubriblast Cytoplasm is moderate in amount with deep basophilia due to high amounts of cytoplamsic RNA Nucleoli are present though not always visible Active mitotic division noted

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Prorubricyte (Basophilic normoblast)

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Polychromatic erythroblast(rubricyte) Cytoplasm stains various shades of gray due to mixture of RNA and hemoglobin Nuclear volume occupies half of the cell area May undergo 1 or mitotic division in which after the last division the nucleus become small & condensed

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Rubricyte (polychomatic erythroblast)

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Orthochromic normoblast(metarubricyte) Last nucleated stage in RBC series First non-mitotic stage Slight polychromasia Abundant or full hemoglobinization

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Metarubricyte (orthochromic normoblast)

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Reticulocyte Non-nucleated immature RBC Appears polychromatic due to remaining RNA responsible for the bluish-gray color on air-dried smears Larger than mature erythrocyte Released into the circulation after 2 days of maturation in the marrow Synthesize Hemoglobin for approximately 1 day after leaving the bone marrow

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Reticulocyte (poychromatophilic erythrocyte)

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Reticulocyte (supravital stain)

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Mature Erythrocyte Appears as a biconcave disc with a concavity on each side – “Discocyte” Average size 7.2 um

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Erythrocyte (mature RBC)

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Granulopoiesis (WBC) Hematopoietic growth factors influencing formation of WBCs Strict lineage: G-CSF (colony stimulating factor) – granulocytes (neutrophils) M-CSF – monocytes Multilineage: GM-CSF – granulocytes, monocytes, megakaryocytes & RBC

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Cells of the WBC series Myeloblast Promyelocyte Myelocyte Metamyelocyte Band or stab Segmenter

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Myeloblast Earliest cell in the WBC series Nucleus:cytoplasm ratio of 4:1 Large, round nucleus with 2-5 visible nucleoli Deeply basophilic cytoplasm No granules noted

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Myeloblast

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Promyelocyte Slightly smaller than myeloblast Basophilic cytoplasm N:C ratio of 2:1 with visible nucleoli Presence of azurophilic granules

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Promyelocyte

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Myelocyte Appearance of the specific granules or also known as secondary granules Specific granules will determine the functional destiny of the WBC giving rise to eosinophil, basophil or neutrophil. N:C ratio 1:1 with almost invisible nucleoli. Cytoplasm show mixture of basophilic and acidophilic staining

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Myelocyte

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Metamyelocyte Also known as the JUVENILE Differentiated from the myelocyte because of the presence of indentation of its nucleus N:C ratio 1:1 and smaller than the myelocyte

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Metamyelocyte (juvenile)

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Band or Stab Also known as the STAFF Measures 12-13 um Nucleus is sausage-shaped, elongated or horse-shoe shaped in appearance there is no lobulation or segmentation noted.

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Band / Stab / Staff

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Segmenter Most mature stage of the WBC N:C ratio of 1:2 Nucleus shows lobulation or segments Differentiated based on the appearance of its granules as follows:- Eosinophil – reddish-orange granules- Basophil – blue-black granules- Neutrophil – pink-tan granules

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Neutrophilic segmenter

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Eosinophil

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Basophil