HEMOPOEISIS FORMATION OF BLOOD CELLS.pptx

hemopoeisis- formation of blood cells
erythropoeisis- formation of RBC
Leucopoeisis- formation of WBC
thrombopoeisis- formation of platelets

1. HEMOPOEISIS PREPARED BY PUNAM SAHOO

2. HEMOPOIESIS Hemo Referring to blood cells Poiesis "The development or production of“ The word Hemopoiesis refers to the production & development of all the blood cells: Erythrocytes : Erythropoiesis Leucocytes : Leucopoiesis Thrombocytes . Thrombopoiesis. Granulopoiesis (or granulocytopoiesis ) is haematopoiesis of granulocytes. Megakaryo cytopoiesis is haematopoiesis of megakaryocytes

3. STEM CELL All cellular blood components are derived from haematopoietic stem cells. In a healthy adult person, approximately million new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation. These cells have extensive proliferative capacity and also the: Ability to give rise to new stem cells (Self Renewal) Ability to differentiate into any blood cells lines (Pluripotency)They grow and develop in the bone marrow. The bone marrow & spleen form a supporting system, called the"hemopoietic microenvironment"

4. Pluripotent Stem cells : Types Pluripotent Stem cells Has a diameter of 18 - 23 μ. Giving rise to: both Myeloid and Lymphoid series of cellsCapable of extensive self-renewal. Myeloid Stem cells : Generate myeloid cells: Erythrocytes Granulocytes: PMNs, Eosinophils & Basophils. Thrombocytes. Lymphoid Stem cells : Giving rise only to: Lymphocytes: T type mainly

5. Sites of Hemopoeisis Hemopoiesis starts as early as yolk sac development. The cells then colonize in the liver,spleen and bone marrow.in the 2 nd trimester of fetal life,the cells are formed in the liver and spleen,by the time of birth the development only takes place in bone marrow. 2-3 weeks after fertilization 3 layers are developed ( ecto , meso , and endoderm)Hemoangioblast which is derived from the mesoderm

6. Stages of Erythropoiesis The red blood cells develop from the burst-forming unit- erythrocyte (BFU-E) and colony-forming unit-erythrocyte (CFU-E) which are derived from the committed progenitor cells.The different stages of erythropoiesis are as under: Pronormoblast or proerythroblast is the earliest recognizable cell of the erythroid series seen in the red bone marrow. Early (basophilic) normoblast (basophilic early erythroblast). The pronormoblast progresses into the early normoblast. Intermediate (polychromatic) normoblast (poly-chromatic erythroblast ). It is the next maturation stage in erythroid seriesHemoglobin appears in this stage. Late (orthochromatic) normoblast (orthochromatic erythroblast) is the last nucleated cell of erythroid series.

7. Continue… Reticulocyte is the last stage in the formation of erythrocytes, that is why it is also called young red cell. Size and shape: The reticulocyte is a flat, disc shaped, slightly larger (7-7.5 µm) than the mature erythrocytes. Cytoplasm still contains small amounts of RNA. With supervital stain such as brilliant cresyl blue, the RNA appears in the form of a reticulum (net-like structure). Because of this character the cell is called reticulocyte. Nucleus is absent Total process takes about 7 days.

8. Regulating factor for erythropoiesis Erythropoiesis is the process of red blood cell production, which is regulated by several factors. These factors include:  Erythropoietin (EPO) : A cytokine secreted by the kidneys in response to low blood oxygen levels. EPO binds to receptors on bone marrow cells, which triggers the production of mature red blood cells.  Hepcidin : A protein produced by the liver that inhibits iron mobilization.  Transcription factors : Such as GATA and KLF, which play a key role in erythropoiesis.  Hypoxia-inducible factors (HIFs) : Transcription factors that increase EPO production, enhance iron uptake, and adjust the bone marrow microenvironment.  MicroRNAs : Small regulatory RNAs that can down-regulate the expression of target genes.  Cortisol : Released from the adrenal glands during stressful conditions, such as sepsis or severe trauma.  Nutritional deficiencies : Such as iron, B12, or folate.  High altitudes : The body secretes more EPO in response to the lower oxygen levels at high altitudes.

9. LEUCOPOEISIS The process of development and maturation of white blood cells (leucocytes) called leucopoiesis is a part of hemopoiesis (formation of blood cells). All the blood cells develop from the so called pluripotent hemopoietic stem cells (PHSCs). The stem cells after a series of divisions differentiate into progenitor cells which are also called colony-forming units (CFU). The leucopoiesis can be discussed under two headings: Formation of granulocytes (granulopoiesis) and monocytes Formation of lymphocytes (lymphopoiesis).

10. Formation of granulocyte and monocyte The granulocytes and monocytes are formed in the bone marrow from the colony-forming unit called CFU-GM (colony- forming unit granulocytes and monocytes): The progenitor cells (CFU-GM) forming different cells are further named as: CFU-G are neutrophil forming units. CFU- Eo refers to eosinophil forming units CFU-Ba are basophil forming units CFU-M refers to monocyte forming units. The development of granulocytes through various stages is called myeloid series and development of monocytes through various stages is called monocyte-macrophage series.

11. Myeloid series Some facts about granulopoiesis. The cells of myeloid series include myeloblast (most primitive precursor), promyelocytes, myelocytes, meta- myelocytes, band forms and segmented granulocyte (mature form). The process of granulopoiesis takes about 12 days. Granulocytes are formed and stored in the bone marrow. When need arises they are released in circulation. Normally about three times or many granulocytes are stored in the bone marrow as these circulate in the peripheral blood.

12. Formation of lymphocyte The lymphocytes are formed from the lymphocyte stem cells which are formed from the pluripotent hemopoietic stem cells (PHSC) in the bone marrow . The lymphocyte stem cells migrate into thymus and peripheral lymphoid tissues where they proliferate and mature into lymphocytes. The tissues which actively produce lymphocytes from the germinal centers of lymphoid follicles as a response to antigenic stimulation constitute the so called secondary or reactive lymphoid tissue. It is comprised of the: Lymph nodes Spleen Gut-associated lymphoid tissue (GALT).

13. Lymphoid Series The maturation stages of lymphoid series are lymphoblast, prolymphocytes and lymphocyte . Prolymphocytes mature successively into large lymphocyte and small lymphocyte, both of which are found in circulation. Then some lymphocytes enter thymus where they are processed and come out as T lymphocytes. Some lymphocytes are processed in liver (in fetal life) and bone marrow (after birth). These come out as B lymphocytes

14. Thrombopoiesis Formation or development of platelets is called thrombopoiesis The platelets are produced in the bone marrow. The pluripotent stem cell destined to form platelets is converted into colony forming units called Meg-CFU, which develop into platelets after passing through various stages . Platelets are formed from pseudopodia of megakaryocyte cytoplasm which get detached into the blood stream. Each megakaryocyte may form up to 4000 platelets. The formation of platelets from the stem cell takes about 10 days. Control of thrombopoiesis Thrombopoiesis seems to be regulated by the following humoral factors : Thrombopoietin Megakaryocyte-colony stimulating activity (Meg CSA).