Erythropoiesi1 - and other organelles and is called a...

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Erythropoiesis Erythropoiesis in the red bone marrow is under the control of erythropoietin . In response to hypoxemia in the blood, the kidneys release EPO into the blood. EPO stimulates the differentiation of hemocytoblasts into erythrocytes. This results in increased production of red blood cells within 3-5 days. The production of erythrocytes requires iron , folic acid and vitamin B 12 , and vitamin C . The process of erythropoiesis has four major developmental changes: a reduction in cell size, an increase in cell number, the synthesis of hemoglobin , and the loss of the nucleus and other organelles . The first committed cell in the erythrocyte pathway is the proerythroblast . The proerythroblast has receptors for EPO; EPO stimulates the development of the proerythroblast into an erythroblast . Erythroblasts undergo mitosis and synthesize large quantities of hemoglobin, sometimes called normoblasts . When complete, the erythroblast discards its nucleus
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Unformatted text preview: and other organelles and is called a reticulocyte . Reticulocytes leave the bone marrow and circulate in the blood; within a day or two, the reticular network disintegrates and the cell is a mature erythrocyte. Normally, about 1% of circulating red blood cells are reticulocytes, but that percentage can increase after hemorrhage. Erythrocytes Erythrocytes are disc-shaped cells with thick rims and a biconcave shape. (See Figure 3). The loss of organelles during maturation significantly increases the surface area/volume ratio and thus the diffusion rate of substances into and out of the cell. The major function of RBCs is gas transport, primarily oxygen and carbon dioxide . The major protein within RBCs is hemoglobin . Carbonic anhydrase is also found in the cytoplasm of RBCs; this enzyme plays a significant role in regulating pH homeostasis. Figure 3...
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