Erythropoiesis is stimulated by the hormone erythropoietin, produced in the kidneys. The hormone is produced in response to low tissue oxygen tension and stimulates stem cells to transform into proerythroblasts. The proerythroblast is a large cell, has a large nucleus, nucleoli and a rim of basophilic (blue) cytoplasm.
Hemoglobin synthesis starts and increases with successive cell divisions. The cytoplasm changes from blue to greyish-pink (polychromatic) as hemoglobin levels increase. The developing normoblasts are classified into early, intermediate and late according to the amount of hemoglobinization, reduction in the size of the nucleus and the overall size of the cell.
When hemoglobinization is complete, the remains of the nucleus is removed and the cell is released into the circulation as a reticulocyte (juvenil red cell). Reticulocytes still contain remnants of cytoplasmic RNA which explains the polychromasia. Reticulocytes mature within 1-2 days into normochromic (pink) cells.
Red blood cell normally survive for 110 days. Old or damaged red cells are removed by phagocytic cells of the reticuloendothelial (RE) system and constituents are re-utilized for production of new cells.
Title : Erythropoiesis
Description : Erythropoiesis is stimulated by the hormone erythropoietin, produced in the kidneys. The hormone is produced in response to low tissue oxyg...
