A1 Hematopoiesis - Hematopoiesis Blood cell production,...

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Hematopoiesis Blood cell production, differentiation, and development
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Reading Assignment McKenzie Organization of the book: pgs 5-7
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Blood cells found in peripheral blood (circulating blood)
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Origin and development of blood cells In the embryo, primitive cells (mesenchymal stem cells) are first formed in the yolk sac These cells differentiate into blood cells
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Embryonic blood cell production occurs in three phases Mesoblastic phase Formation of blood islands that carry on fetal erythropoiesis 2 nd and 3 rd month of gestation Embryonic hemoglobins: Gower I, Gower II, Portland Hepatic phase Production of rbcs in liver (primarily). Also spleen, thymus and lymph nodes Granulocytes and megakaryocytes (precursors of platelets) begin production 4 th and 5 th month of gestation Embryonic hemoglobin : hemoglobin F (fetal)
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Cell production: cont. Myeloid phase Bone Marrow takes over cell production (myelopoiesis) 5 th month of gestation Lymphocytes (including plasma cells) are produced in lymph and spleen throughout life (extramedullary production) Hemoglobin : A (adult hemoglobin) produced 3 weeks postpartum Shortly after birth, extramedullary production of red cells and granulocytes (neutrophils, monocytes, eosinophils and basophils) ceases
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After bone marrow (BM) takes over production of blood cells, the primitive mesenchymal stem cells are reduced They persist throughout life as part of the reticuloendothelial (RE) system RE system: bone marrow, liver, spleen, lymph nodes The stem cells remain active in the BM but are inactive in other parts of the RE system If needed (BM damage, increased need of cells production) these dormant stem cells can become active and produce cells (extramedullary hematopoiesis)
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Red marrow vs yellow marrow During the first few years of life, the infant bone marrow space is limited and all is used for cell production In the infant hematopoiesis occurs in the bone marrow of all bones By the 4 th year the bone marrow growth exceeds the need for blood cells, and marrow sites are replaced with fat cells The amount of fat increases with age. By the age of 18 years ½ is red and ½ is yellow marrow A 70 y/o has marrow containing about 2/3 yellow and 1/3 red marrow
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hematopoiesis becomes confined to the
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This note was uploaded on 08/02/2011 for the course HEMATOLOGY 101 taught by Professor Smith during the Fall '09 term at Navarro College.

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A1 Hematopoiesis - Hematopoiesis Blood cell production,...

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