Erythropoiesis Final 2025 PDF

Erythropoesis By Dr Horeya Erfan Korayem :Objectives Describe the LM structure of bone marrow including all its components Differentiate between the LM structure of the yellow and red bone marrow Describe and draw the stages of development of blood cells hem...

Erythropoesis By Dr Horeya Erfan Korayem :Objectives Describe the LM structure of bone marrow including all its components Differentiate between the LM structure of the yellow and red bone marrow Describe and draw the stages of development of blood cells hematopoiesis including: erythropoiesis Relate the structure of the bone marrow to its function  Bone marrow Definition :Is gelatinous, vascular , cellular CT in marrow cavities Site: ribs, vertebrae, pelvis, epiphyses and shoulder girdle Function: hemopoesis 5th month prenatal Types:  Red bone marrow: active cellular, rich RBCs  Yellow bone marrow :infiltrated with fat  Bone marrow 1. Red (active) marrow 2. Yellow (inactive) marrow Bone marrow  Bone marrow Structure:  Sinusoid: Provide the barrier between the hemopoietic compartment and the peripheral circulation. 45-88µm diameter Lined by endothelial cells with large gaps (pores) between them, so basement membrane is discontinuous. Surrounded by thread of reticular F& processes of adventitial reticular cells Bone marrow  Bone marrow  Stroma cells Fat storing cells Macrophages:  Destroy exruded nuclei of RBCs  Excess cytoplasm  Malformed cells Adventitial (reticular) cells:  Branched  Provide some support for the developing blood cells  Resemble fat cells accumulate fat help in transforming red to yellow bone marrow  Parenchyma : Island of hemopoetic cells suspended: in different stages of development  Bone marrow Megakaryocytes: are the most prominent cells (huge size + multilobed.nuclei) up to 150 μm in diameter  Bone marrow :Functions of the bone marrow 1. Production of the blood cells. 2. Removal of aged or defective RBCs by sinusoidal macrophages. 3. Storage of iron resulting from hemoglobin breakdown. 4. Differentiation of B-lymphocytes  Bone marrow Yellow bone marrow Not active in blood cell formation contains predominately adipose cells It is not hemopoietic, but it has the potential to become so if necessary. Site: long bones of the arms, legs, fingers, and toes  Bone marrow Item Red bone Yellow bone marrow marrow Feature Color is red due yellow due to its to red due to its high content of - high content of fat cells HB (in RBCs) Function Haematopoesis It is not hemopoietic, but it has the potential to become so if necessary. Cell type ??????????? predominately adipose cells Location ribs, vertebrae, long bones of the pelvis, epiphyses arms, legs, and shoulder fingers, and toes girdle  Hemopoesis Hemo: referring to blood cells Poesis: development or production of Hemopoesis refers to the production & development of all blood cells Erythropoesis: erythrocytes (RBCs) Leucopoesis: leucocytes Thrombopoesis: thrombocytes (platalets)  Erythropoiesis Process of development , differentiation & maturation of RBCs from primitive stem cells  Erythropoiesis Stages of hematopoesis Mesoblastic stage (2nd wk intrauterine) Hepatic stage (6th wk intrauterine up to birth): in liver & spleen Myeloid stage (5th months): bone marrow Child: BM in cavities of all bones Adult (20 years): ends of long bones(femur, tibia), vertebrae, sternum & ribs Erythropoiesis Erythropoiesis  Erythropoiesis Hematopoeitic stem cell Stem cell: extensive proliferation capacity Character: markers  CD34, p170 pump & c-kit (receptor molecule for stem cell factor)  Homebox genes: early stages Erythrocytes:Hox2 Myeloid:Hox1 Site : Bone Marrow Function: Self renewal: ability to give new stem cell Pluripotency: differentiate into any blood cell lines  Erythropoiesis Blood Stem-cells 1. Pluripotential stem cells. 2. Multipotential stem cells 3. Progenitor cells. 4. Precursor cells  Erythropoiesis Pluri-potential stem cells 0.1% nucleated cell population of bone marrow They are similar to small lymphocytes Undergo cell division – Self renewal – Multi-potential stem cells (CFU)  Erythropoiesis Multi-potential stem cells (CFU) Capable for extensive proliferation. They are also called colony-forming unit (CFU) cells. They are similar to small lymphocytes.  Erythropoiesis Hemopoietic stimulating factor Erythropoeitin: which is secreted by the kidneys, mostly in response to hypoxia IL3 & IL9: erythrocyte Steel factor(stem cell factor): which is secreted by bone marrow stromal cells act on pluri, multipotential & unipotential stem cells Erythropoiesis  Erythropoiesis Pluripotent hematopoetic stem cell PHSCs Self renewal M Colony Growth H factor forming unit C s Colony Colony forming forming Unit-S Unit-LY Progenitor cells Precursor cells Proerythroblast -Granulo cytes Monocytes Platelets  Erythropoiesis 1. Erythroid progenitor cells  Burst-forming unit-erythroid (BFU-E) has a high rate of mitotic activity  CFU-E: which arises from BFU-E; responds to low concentrations of erythropoietin and gives rise to the first histologically recognizable erythrocyte precursor, the proerythroblast. 2. Erythrocyte precursor cells include a series of cell types ( the erythroid series) that differentiate sequentially to form mature erythrocytes  Erythropoiesis Progenitor cells Precursor cells Unipotential Arise from progenitor cells Committed to single cell No self renewal line Express morophological Self renewal ↓ character of 1st cell of cell line (proerythroblast) Cell differentition to mature cells  Erythropoiesis A process that proceeds by differentiation and maturation of RBCs. It includes: 1.Progressive reduction in the size of the cells. 2.Formation of hemoglobin. 3.Extrusion of the nucleus. Erythropoiesis  Erythropoiesis Pro-erythroblast: Larger cell with large rounded nucleus.(12-15µm) The nucleus is large with fine chromatin and large prominent 2 nucleoli. The cytoplasm is slightly basophilic because of the presence of free ribosomes.  Erythropoiesis Basophilic erythroblast: Size: Smaller (11- 13µm) Cytoplasm: more basophilic because of the large number of free ribosomes (polyribosomes) that synthesize hemoglobin. Nucleus: small &condensed more heterochromatic  Erythropoiesis Polychromatophil erythroblast: Size: (9-11 µm) Cytoplasm: violet (bluish pink) gray or lilac color to the cytoplasm, or distinct pink (acidophilic) and purple (basophilic) regions may be resolved in the cytoplasm. Acidophilia due to Hb synthesis by the cell Nucleus: smaller& deeply basophilic by  Erythropoiesis Orthochromatophil erythroblast (Normoblast): Size: (6-9 µm) Cytoplasm: acidophilic Acidophilia due to Hb synthesis by the cell &loss RNA Nucleus: smaller, eccentric& deeply stained pyknotic This cell ejects its nucleus which is then  Erythropoiesis Reticulocyte: No nucleus Has a small number of polyribosomes that, when treated with the dye brilliant cresyl blue, form a faintly stained network. Reticulocytes pass to the circulation (where they may constitute 1% of the red blood cells), quickly lose the polyribosomes, and mature as erythrocytes.  Erythropoiesis It appears in the peripheral circulation in a percentage < 1% of mature RBCs. High reticulocytic count: In case of hemorrhage, hemolytic anaemia & high altitudes. Low reticulocytic count: As an indication of improvement in patients suffering from blood loss or hemolytic anaemia.  Erythropoiesis Erythrocytes: Size: (6-9 µm) Cytoplasm: acidophilic Acidophilia due to Hb synthesis by the cell &loss RNA No nucleus Erythropoietin is produced primarily in which organ? A. Liver B. Kidneys C. Bone marrow D. Spleen 3. The hormone erythropoietin primarily acts on which of the following cells? a) Myeloid stem cells b) Lymphoid stem cells c) Proerythroblasts d) Plasma cells Which of the following stages comes just before the mature erythrocyte in erythropoiesis? a) Proerythroblast b) Basophilic erythroblast c) Reticulocyte d) Normoblast During erythropoiesis, at which stage does the cell lose its nucleus? a) Basophilic erythroblast b) Polychromatic erythroblast c) Orthochromatic erythroblast d) Reticulocyte