erythropoiesis-I_mechanism& clinical significance.pptx

RBC Generation. Source

1. DEFINITION OF ERYTHROPOIESIS, SITE OF ERYTHROPOIESIS AND PROCESS OF ERYTHROPOIESIS

2. Dr. E. Muralinath

3. DEFINITION Erythropoiesis is defined as the process of the origin, development and maturation of particularly erythrocytes. 2)Whereas Hemioiesis or Hematopoiesis is dfefined as the process of rigin, development and maturastion of especially all the blood cellsd

4. SITE OF ERYTHROPOIESIS   IN FETAL LIFE In fetal life, erythropoiesis happens in three stages. MESOBLASTIC STAGE: During the first two months of intra uterine life, the production of the RBCs happens from mesenchyme of yolk sac. B) HEPATIC STAGE: From third month of intra uterine life, the production of RBCs takes place in the liver which is the main organ. 2)An involvement of spleen and lymnphoid organs happens during the process of erythropoiesis. MYELOID STAGE During last three months of intra uterine life, the production of RBCs takes place from red bone marrow as well as liver.

5. IN NEW BORN BABIES, CHILDREN AND ADULTS: In the new born babies, growing children and adults, the production of RBCs takes place from only from the red bone marrow. UPTO THE AGE OF 20 YEARS: The production of RBCs happens from red bone marrow of all bones (long bones as well as the flat bones) AFTER THE AGE OF 20- YEARS The production of RBCs takes place from membranous bones like iliac bones, ribs,scapula , skull bones, sternum and from the ends of long bones. After the 20 years of age, the shaft of long bones is converted into yellow bone marrow due to fat deposition and loses the erythroipoietc ability.

6. IN ADULTS: The production of the blood cells takes place in liver and spleen because of the destruction or fibrosis of the bone marrow. B)Collectively the size as well as weight of bone marrow is almost equal to liver.Bone marrow is also as active as liver. C) Even though, bone nmarrow is the site of production of all blood cells, an involvement of 75% of the bone marrow happens regarding the production of leukocytes and only 25% regarding the production of erythrocytes. D)The number of leukocytes are less in number compare to the erythrocytes , the ratio being 1 : 500.This is primarily due to the span of thee cells.m Life span of erythrocytes is 120 days whereas lifespan of leukocytes is very less ranging from one to days approximately. That is why, the leukocytes require more production compare to erythrocytes to regulate the required number.

7. PROCESS OF ERYTJROIPOIESIS: STEM CELLS: Stem cells are treated as primary cells and thee cel;ls are capable of self-renewal differentiating into specialized cells. Hemopoietic stem cells are the priomitive cells in the bone marrow which yield the blood cells. The hemopoietic stem cells in the bone marrow are treated as uncommitted pluri potent hemopoietic stem cells (PHSC). PHSC is defined as a cell that can result in all types of blood cells. Particularly in early stages, the PHSC is not designed to to form a particular type of blood cell and it is not possible to estimate the blood cells to be developed from these cells, hence the name uncommitted PHSC. In adults, only a few number of these cells are onserved , but the best source of these cells is the umbilical cord blood. If the cells are designed to form to form a particiuilar type of blood cells, theuncommitted PHSCs are termed as committed PHSCs. Committed PHSC is defined as a cell which is limited to produce one group of blood cells.

8. TYPES OF COMMITTED PHSCs Lymphoid stem cells (LSC) which yield lymphocytes as well as natural killer (NK) cells. Colony forming blastocytes, which yield myeloid cells.Myeloid cells are blood cells other than lymphocytes. If grown in cultures, thee cells are helpful in forming colonies, hence the name colony formimg blastocytes.

9. DIFFERENT UNITS OF COLONY FORMING UNITS: Colony Forming Unit - Erythrocytes (CFU-E): The cells of this unit form into erythrocytes. Colony Forming Unit - Granulocytes / Monocytes (CFU - GM). These cells yield granulocytes (neutrophils, basophils and eosinophils and Monocytes. Colony Forming Unit- Megakaryocytes (CFU-M) The development of Platelets takes from these cells.

10. CHANGES DURING ERYTHROPOIESIS The cells of CFU - E undergo various stages and fully develop into matured RBCs. During these stages four important changes are observed. Reduction in size of the cell ( from the diameter of 25 to 7.2 microns) Absence of nucleus as well as nucleoli Modifications rergasrding the staining properties of the cytoplasm.

11. STAGES OF ERYTROPOIESIS The different stages between CFE - U and the matured RBC are Proerythroblast Early normoblast Intermediate normoblast Late normoblast Reticulocyte Matured erythrocyte

12. PROERYTHROBLAST (MEGALOBLAST):- It is the first cell derived from CFU - E. It is very large in size along with a diameter of approximately about 20 microns. The nucleus of this cell is very large and covers the cell completely. The nucleus exhibits two or more nucleoli and a reticular network. Hrmoglobin is absent in the Proerythroblast. The cytoplasm resembles basophilic in nature. The Proerythroblast multiplies many times and lastly forms the cell of next stage is termed as Early Norrmoblast.

13. EARLY NORMOBLAST: It is slightly smaller compare to proerythroblast and it exhibits a diameter of approximately 15 mivrons. In the nuceus, the nucleoli is absent Condensation of vhromatin network takes polace The condensed network shows more density. The cytoplasm is basophilic in nature. That is why, this cell is also tertmed as basophilic erythroblast. This cell changes into next stage termed as Intermediate Normoblast.

14. INTERMEDIATE NORMOBLAST: This cells shows small size compare to early normoblast and this cell exhibits a diameter of approximately 10 to 12 microns. The nucleus is seen, but the chromatin network exhibits furtyher condensation. The hemogl;obin begins appeariong. The cytoplasm is alrerady basophilic. Now, due to the presence of hemoglobin, it srtains specifically with both acidic and basic stains. So this cell is termed as Polychromatophilic or Polychromatic Erythroblast. This cell changes into nexty stage known as Late Normoblast.

15. LATE NORMOBLAST; The diameter of this cell reduces further to approximately 8 to 10 microns. Nucleus is very small size along with very much condensed chromatin network and it is termed as Ink Spot Nucleus. An enhancement of hemoglobin happens. The cytoplasm almost becomes acidophilic. That is why, the cell is now termed as Orthtochromatic Erythroblast. In the beginning stage of late normoblast just before it undergoes into next stage, the nucleus disintegrstes and disappears. The process by which nucleus disappears is termed as Pyknosis. An extrusion of final remnant happens from the cell. Late Normoblast grows into next stage known as reticulocyte.

16. RETICULOCYTE: It is otherwise termed as immature RBC. It is slightly larger compare to matured RBC. The cytoplasm consists of reticular networks or reticulum which is formed by espoecially remnants of disintegrated organelles. Because of the reticular network, the cell is termed as reticulocyte. The reticulum of reticulocyte stains particularly with suprtavital stain. In newborn babies, the reticulocyte count is approximately 2-6% of RBCs. That is 2to 6 reticulocytes are seen for every 100 RBCs. The number of reticulocytes reduces during first week after birth. Later, the reticulocyte count remains constant at or below 1% of RBCs. The number enhances, whenever production and release of RBCs enhance. The reticulocyte is basophilic because of the presence of remnants of disintegrated Golgi bodies, mitochondria and other organells of cytoplasm. During this stage, the cells enter the capillaries through the capillary membrane especially from source of production by diapedesis.

17. MATURED ERYTHROCYTE The disappearance of reticular network takes place and the cell becomes the matured RBC and gets the biconcave shape. The reduces in size approximately to 7.2 microns diameter. The matured RBC consists of hemoglobin but the nucleus is absent. It needs seven days especially for the development of RBC from proerythroblast. It needs five days upto the stage of reticulocyte. The reticulocyte requires two or more days to become the matured RBC