Week 4 Day 2 Erythropoiesis PDF

ERYTHROPOIESIS 1 ERYTHROPOIESIS It’s a regulated process of RBCs production Erythropoiesis occurs in the BM Erythron: It’s the entire mass of mature & immature RBC’s in the body There is a balance between RBC’s production & destruction....

ERYTHROPOIESIS 1 ERYTHROPOIESIS It’s a regulated process of RBCs production Erythropoiesis occurs in the BM Erythron: It’s the entire mass of mature & immature RBC’s in the body There is a balance between RBC’s production & destruction. https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.shutterstock.com%2Fsearch %2Ferythropoiesis&psig=AOvVaw2mSpAceExn5EfSW0JuQx49&ust=1725741251495000& source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCPiBz6aVr4gDFQAAAAAd AAAAABAR  ERYTHROPOIESIS 2 PROCESS OF ERYTHROPOIESIS Proliferation: The division of immature cells to produce increased numbers of more mature cells. Maturation The development of cells through early, intermediate & late stages.  ERYTHROPOIESIS 3 THREE POINTS OF CONTROL OF ERYTHROPOIESIS Control of the self-replication of progenitor cells Control the movement of mature cells from bone marrow into blood A feedback control on cell production.  ERYTHROPOIESIS 4 STAGES IN THE DEVELOPMENT OF ERYTHROCYTES  ERYTHROPOIESIS 5 PROERYTHROBLAST/ pronormoblast Earliest recognizable erythroid cell in the bone marrow Size (12 - 20 µm) Round nucleus centrally placed within the cell with visible nucleoli & chromatin strands that are dispersed Cytoplasm is usually only a narrow rim around the large nucleus, deep blue (RNA) when stained by Romanowsky dyes  ERYTHROPOIESIS 6 EARLY ERYTHROBLAST/EARLY NORMOBLAST/BASOPHILIC NORMOBLAST Slightly smaller than Pronormoblast Size: 10 - 16 µm in diameter. Nucleus: occupies less of the cell & does not contain nucleoli with more condense chromatin Cytoplasm: predominant color is blue (RNA) with little pinkish color This is a sign that Hb, which stains pink, is being produced & the RNA & protein synthetic apparatus is being  ERYTHROPOIESIS 7 POLYCHROMATIC NORMOBLAST / INTERMEDIATE NORMOBLAST Smaller than basophilic normoblast but with twice amount of Hb Cell size: 8 - 14 µm in diameter. Nucleus is smaller & denser. Nuclear chromatin is condensed Cytoplasm shows a polychromatic staining reaction. Pinkish color predominate This means that it takes both the acid & basic stains producing a purple-pink color. Normally not seen in PB  ERYTHROPOIESIS 8 ORTHOCHROMATIC NORMOBLAST/NUCLEATED RBC Size: has a diameter of 8 - 10 um Nucleus is eccentric, small, solid & blue black with clumped chromatin Cytoplasm predominantly pinkish (Hb) Mitochondria are no longer evident Normally not seen in PB  ERYTHROPOIESIS 9 POLYCHROMATOPHILIC ERYTHROCYTE / RETICULOCYTE A young RBC that still contains some fine basophilic material bluish stain (RNA remnant) Size: 8 - 10 µm in diameter Nucleus is extruded Retics is released to blood, there it needs (1-2) days before maturation Normally, rarely found in PB Retics can be stained with a supravital stain as brilliant cresyl blue or new methylene blue, by which reminant RNA is stained blue & appear as filaments or granules  ERYTHROPOIESIS 10 MATURE ERYTHROCYTES Biconcave disc with circular outline (7 - 8) µm in diameter. (1.5 - 2.5) µm in thickness Stained pink (Hb) Paler central area (2-3) μm No nucleus or mitochondria Life span: 120 days  ERYTHROPOIESIS 11 MATURE ERYTHROCYTES Each pronormoblast divides into 14 – 16 mature RBCs RBCs production takes about 10 days from the pluripotent stem cell to the mature RBCs. From reticulocyte to fully mature RBCs,  ERYTHROPOIESIS 12 REGULATION OF ERYTHROPOIESIS Erythropoiesis is regulated by the hormone erythropoietin (EPO) by increasing number of progenitor cells committed to erythropoiesis. The human erythropoietin gene is located on chromosome 7. EPO is produced by (90% kidney & 10% by the liver) Oxygen level in kidney’s tissues controls EPO production. When O2 supply to renal tissue falls, EPO levels increase When O2 supply to renal tissues increases, EPO levels falls  ERYTHROPOIESIS 13 OTHER FACTORS NECESSARY FOR ERYTHROPOIESIS It must be remembered that although erythropoietin (EPO) plays a critical role in RBCs production, other factors are also necessary for the formation of fully functioning cells. The main ones are listed below: 1. Metals: iron & cobalt 2. Vitamins: Vitamin B12,folic acid & vitamin (B6 pyridoxine) 3. Hormones: Stem Cell Factor (SCF), IL-3 &  ERYTHROPOIESIS 14 RETICULOENDOTHELIAL SYSTEM (R.E.S.) R.E.S. consists of the spleen, liver & bone marrow. RE cells “macrophages” destroy RBCs by process of phagocytosis. This mechanism is called “extravascular Destruction” of the red cell. On average, 1% of the body’s RBCs are destroyed & replaced each day. This means that 2.5 million cells are replaced each day by bone marrow.  ERYTHROPOIESIS 15 INEFFECTIVE ERYTHOPOIESIS Normally: Some of immature RBC’s don’t develop normally in BM (1-15%). So, they don’t reach maturity & circulation. They are removed by macrophages in BM. In ineffective erythropoiesis: Number of these cells (not developing into mature RBC’s) abnormally increase ˃ 15%.