ERYTHROPOIESIS

 Definition:-erythropoiesis is the process which involves origin, development and maturation of erythrocytes.

Hemopoiesis/hematopoiesis:-it is the process which includesorigin, development and maturation of all the blood cells.

Process of erythropoiesis

Stem cells: - stem cell is the primitive cells in the bone marrow. Which give rise to all blood cells. Stem cell is capable to both self-renewal and differentiation.

                                          

Stages of erythropoiesis :-  6- stage of erythropoiesis 

1. proerythroblast              -          20 μ size

-          Nucleus present and very large

            -          Hb absent.

2. Early normoblast           -        12-15 μ size 

-         Nucleus present 

 -         Hb absent.

3. Intermediate normoblast   -         10-12 μ size

      -          Hb – present

      -          Nucleus – present

Note: - In 3 stage the Hb – is present.

4. Latenormoblast                 -          8-10 μ size

    -          Hb present

    -          Nucleus absent

Note: - In - 4 stages nucleus is absent this process is known as pyknosis. 

5. Reticulocyte/Immature RBC    -             8 μ size

-              Nucleus absent

-              Hb – present.

Note: - In new born babies reticulocyte count is 2 to 6% of RBC. This present decrease during first week after birth so excess destruction of immature RBC leads physiological jaundice in new born. Later the reticulocytes count remains constant below the 1% of RBC.

6. Matured erythrocyte              -         7.2 μ size

                                                       -          Nucleus – absent

                                                       -          Hb – present 

Note: - 7 – days requires for development and maturation of RBC from proerythroblast. It requires 5 – days up to stage of reticulocyte. The reticulocytes take 2 – days to become matured RBC.

General factors necessary for erythropoisis :- 

1. Erythropoietin: - secretes from kidney. 

Works: -  it stimulates the bone narrow to production of RBCs. 

2. Thyroxine:-itsecrete from thyroid gland.

Work: - accelerates the process of erythropoiesis at many levels.

Note: - hyperthyroidism leads – polycythemia.

3. Vitamins:- vita. B,C,D,E is necessary for the process of erythropoiesis. 

Maturation factors: -vita B12, intrinsic factor, folic acid necessary for the maturation of RBC. 

1. Vita B12 (Cyanocobalamin) :- this is essential for maturation of erythrocytes. For the absorption of vita. B12the intrinsic factor is necessary. The deficiency of vita – B12leads pernicious anemia.

2. Intrinsic factor: - it is produced in gastric mucosa and it is essential for the absorption of vita. B12. 

3.Folic acid: - it is required for synthesis of D.N.A in the absence of folic acid the synthesis of D.N.A decrease. This leads anemia in which the cells are large this leads megaloblastic anemia.