Module 4 RBC Maturation and Function Acknowledgments Ministry of Health Guyana Centers for Disease Control and Prevention CDC Global AIDS Program GAP Guyana Centers for Disease Control and Prevention CDC Atlanta American Society for Clinical Pathology ASCP Objectives Review the origin of blood cells using the present stem theory of haematopoiesis Describe factors involved in the regulation of erythropoietic activity including substances needed for erythropoiesis and haemoglobin synthesis Discuss the site of synthesis of erythropoietin and its influence on erythropoiesis List two nomenclatures used to describe the stages of RBC maturation Objectives Differentiate each cell in the RBC maturation series based on cell size nuclear size cytoplasmic color and nuclear chromatin Describe the reticulocyte including its composition time spent in the bone marrow and in the blood circulation Discuss the mature erythrocyte including Function and normal lifespan Membrane characteristics Energy pathways Destruction Objectives Discuss the spleen s role in monitoring red cell deformability Correlate normal and abnormal RBC size and haemoglobin content with MCV MCH and MCHC values Calculate the RBC indices including MCV MCH and MCHC Stem Cell Theory of Haematopoiesis Pluripotential stem cells give rise to multipotential progenitor cells Produce unipotential committed stem cells with receptors for specific growth factors Myeloid stem cell and Lymphoid stem cell Respond by division and maturation precursor stages Erythropoietin sensitive committed stem cells CFU E red cells Erythropoietin is lineage specific and regulates RBC production First recognizable bone marrow precursor is the blast following division and maturation of cells Stem Cell Theory of Haematopoiesis Erythropoiesis Normal RBC and Hgb production requires amino acids iron folic acid vitamins B12 and B6 Erythropoiesis is controlled by the rate of oxygen delivery to the tissues Regulated by erythropoietin EPO released by the kidneys in response to hypoxia also androgens EPO stimulates RBC committed stem cells With normal conditions 1 of red cells in the blood are newly released reticulocytes that replace a daily red cell loss of 1 Retics remain in the marrow 2 days before release Normoblastic Erythrocyte Maturation Bone Marrow Four nucleated RBC stages 1 4 Marrow Blood Reticulocyte 5 Stage after nucleus extruded circulates 1 day in blood 9u size residual RNA called polychromasia on Wright s stained smear amount indicates RBC production rate Blood Mature RBC 6 7u size fully haemoglobinized lifespan 120 days Six Stages of RBC Maturation 1 2 3 4 Abbott Manual 5 6 Normoblastic Erythrocyte Maturation Rubriblast Prorubricyte Rubricyte Metarubricyte Reticulocyte Mature RBC Bone Marrow NRBC Polychromasia Mature RBC RBC Precursors Stages Bone Marrow Wright s stained blood smear Wright s Stained Blood Smear Nucleated RBC Mature RBCs Young RBC with Polychromasia Young RBC with Polychromasia Effective Erythropoiesis Mature RBC Functions in oxygen transport and CO2 removal Lacks a nucleus and organelles Must maintain membrane integrity Requires cellular energy and normal haemoglobin Membrane is a protein shell coated with lipids Shape essential to oxygen exchange and deformability Controls volume through control of Na and K Two major energy pathways Embden Meyerhoff ATP membrane Hexose Monophosphate NADPH keeps GSH reduced Mature RBC Energy Pathways Two minor energy pathways Methaemoglobin reductase Fe 3 Fe 2 Rapoport Leubering 2 3 DPG RBC Destruction Normal red cells circulate 120 days With age Enzymes are used up Membrane fragments are lost Leads to spherocytosis removal Normally 90 of red cell removal occurs in the spleen liver extravascular haemolysis Normal deformable RBCs Rigid spherocytes Spleen Functions The spleen functions to Remove RBC inclusions pitting Trap rigid RBCs culling Remove excess lipid from retics grooming Stores sequesters platelets 20 Filters antigens Post Splenectomy Blood Findings Target cell NucRBC Pappenheimer bodies target cell Wright s stained blood smear Howell Jolly bodies Howell Jolly body RBC Indices Define size and or hgb content of red cells Used to classify types of anemia and correlate with the appearance of red cells on blood smear Indices include MCV mean cell volume fl MCH mean cell haemoglobin pg MCHC mean cell haemoglobin concentration Calculated using RBC HGB and HCT values and reported to nearest tenth Indices are average mean values RBC Indices MCV average RBC size varies with age Normal adult MCV 82 98 fL normocytic red cells MCV 82 fL microcytic red cells MCV 98 fL macrocytic red cells Normal newborn 110 fL normal children 77 fL MCH varies with RBC size and Hgb content MCHC average hgb concentration per RBC Normal 32 36 normochromic red cells MCHC 32 red cells may be hypochromic RDW index of RBC size variation Normal 10 14 low RDW uniform RBC size A high RDW indicates anisocytosis RBC Indices Variations in RBC Size and or Hgb Content Color Variations in RBC Size and or Hgb Content Color Normocytic RBCs Microcytic RBCs Macrocytic RBCs Hypochromic RBCs Spherocytes Small lymph Normochromic RBCs Evaluation 3 adults 1 Normocytic normochromic anemia leukopenia thrombocytopenia 2 Microcytic hypochromic anemia leukocytosis thrombocytosis 3 Macrocytic normochromic anemia normal WBC PLT Summary Factors involved in the regulation of erythropoietic activity site of synthesis of erythropoietin and its influence on erythropoiesis Stages of RBC maturation each cell in the RBC maturation series based on cell size nuclear size cytoplasmic color and nuclear chromatin Normal and abnormal RBC size and haemoglobin content with MCV MCH and MCHC values RBC indices calculations including MCV MCH and MCHC