2. Erythropoiesis Learning outcome; By the end of the instructions in this topic the learner should be able to differentiate cells in various stages of erythropoiesis.

3. Objectives By the end of the topic the learner should be able to: Describe the characteristics of blast cells in all stages of erythropoiesis. Draw the structures of all red blood cells in erythrocytic series. Explain the maturation series of erythroblast.

4. What is erythropoiesis? Think!

5. Erythropoiesis: What is it? This is the process through which red blood cells are formed in the body.

6. How does it come about? The process of erythropoiesis begins when there is reduction in Hb concentration in circulating blood. The reduction of Hb will lead to changes in tissue O 2 tension within the kidney. In response to hypoxia, it secretes a hormone called erythropoietin.

7. This hormone induces the primitive stem cell in the bone marrow to differentiate into erythroid cells. This stem cell gives rise to two daughter cells, totipotential and haemocytoblast. Haemocytoblast is committed and differentiates into a pronormoblast due to the stimulus received from erythropoietin.

8. Pronormoblast: recognition The first recognizable cell is the pronormoblast. When stained: Nucleus is round and occupies most of the cell. Has one or two nucleoli. Cytoplasm is deep blue and small in size. Nucleus Cytoplasm Nucleoli

9. A pronormoblast will mature and develop into orthochromatic normoblast.

10. Orthochromatic normoblast When stained: Nucleus is eccentric and small. Stains blue- black. Cytoplasm is large and acidophilic (Hb) Cytoplasm nucleus

11. Orthochromatic normoblast matures and develops into reticulocyte.

12. Reticulocytes – supra vital stain None-nucleated. Larger than mature Rbcs. Are flat disc shaped cells. Also called polychromatophilic cells. Reticulocyte

13. The reticulocytes will mature and develop into mature red blood cells.

14. Red blood cells None-nucleated cells. Biconcave in shape. Cytoplasm has paler centre occupying a 1/3 of cell area. Measure 6.7-7.7micro meter in diameter. The outline is regular. Released in circulation by a process called diapendesis. RBCs

15. And finally!!!!!!!!!!!!……………… I hope you have learned! Goodbye!