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Red Blood Cell Formation - Erythropoiesis stages

Red Blood Cell Production Process is called Erythropoiesis which occurs in Bone Marrow. You can find here Presentation Notes on Stages of Erythropoiesis in word / .ppt /.pdf Format

STAGES OF ERYTHROPOIESIS

The various stages between stem cell and matured red blood cell are as follows :

1    Proerythroblast
2.   Early normoblast
3.   Intermediate normoblast
4.   Late normoblast
5.   Reticulocyte and
6.   Matured erythrocyte.



1. PROERYTHROBLAST (MEGALOBLAST)
This is the first cell derived from the stem cell (CFU-E). It is also called megaloblast. It is very larger in size with a diameter of about 20 microns. Its nucleus is large and occupies the cell almost completely. The nucleus has two or more nucleoli and a reticular network. The proerythro­blast does not contain hemoglobin. The cytoplasm is basophilic in nature. The proerythroblast multiplies several times and finally forms the cell of next stage called early normoblast.

2.  EARLY NORMOBLAST
This cell is slightly smaller with a diameter of about 1; microns. In the nucleus, the nucleoli disappear. Condensation of chromatin network occurs. The condensed network becomes dense. The cytoplasm is basophilic in nature and stains with basic dyes. So, this cell is also called basophilic erythroblast. This cell develops into intermediate normoblast.

3.  INTERMEDIATE NORMOBLAST
This cell is smaller than the early normoblast with the diameter of 10 to 12 microns. The nucleus is still present But, the chromatin network shows further condensation. The hemoglobin starts appearing.The cytoplasm is already basophilic. Now, because of the presence of hemoglobin, it stains with both acidic as well as basic stains. So this cell is called polychromophilic erythroblast. This cells develops into late normoblast.

4. LATE NORMOBLAST
The diameter of the cell is further reduced to about 8 to 10 microns. Nucleus becomes very small with very much condensed chromatin network and it is known as ink spot nucleus.
Quantity of hemoglobin increases. And the cytoplasm becomes almost acidophilic. So, the cell is now called orthochromic erythroblast. In the late normoblast, the nucleus disintegrates and disappears. The process by which nucleus disappears is called pyknosis. The final remnant is extruded from the cell. Late normoblast develops into reticulocyte.

5. RETICULOCYTE
This is otherwise known as immature red blood cell. It is lightly larger than matured red blood cell. The cytoplasm contains the reticular network or reticulum formed by remants of disintegrated organelles. Due to the reticular network, the cell is called reticulocyte. The reticulum of reticulocyte is stained by supravital stain. In newborn babies, the reticulocyte count is 2 to 6%, i.e 2 to 6 reticulocytes are present for every 100 red blood cells. The number of reticulocytes is reduced during the first week after birth. Later, the reticulocyte count remains constant at or below 1 % of red blood cells. The number  may increase whenever there is increased production and release of red . blood cells into the circulation. The reticulocyte is also basophilic due to the presence remnants of Golgi apparatus, mitochondria and other organelles of cytoplasm. During this stage, the cells can enter the capillaries through the capillary membrane from source of production. The cells enter the blood through capillary membrane by means of a process called diapedesis.

6.MATURED ERYTHROCYTE                                                       
Now the reticular network disappears and the cell becomes the matured red blood cell. The matured red cell is biconcave and it is smaller in size with a diameter of 7.2 microns. It attains the biconcave shape, hemoglobin and without nucleus. It requires seven days for the development of matured red blood cell from proerythroblast. It takes five days for development of reticulocyte. The reticuloctye takes two more days to become the matured red blood cell.

Download Notes on Red Blood Cell Formation

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