Haematopoiesis (from Ancient Greek: haima blood; poiesis to make) (or hematopoiesis in the United States; sometimes also haemopoiesis or hemopoiesis) is the formation of blood cellular components. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products All of the cellular components of the blood are derived from haematopoietic stem cells. Hematopoietic stem cells (HSCs are Stem cells that give rise to all the blood cell types including Myeloid ( Monocytes and Macrophages, Neutrophils The term multipotent refers to the ability of a cell to become several different types of cell (but not all types in a germ layer). Multipotent haematopoietic cells can become any type of cell in the blood system. The multipotent cells determine what type of cell to become, or differentiate, in a step-wise fashion. It normally goes at a speed of 1011–1012 cells per day [1]
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Hematopoietic stem cells (HSCs)
Hematopoietic stem cells (HSCs) reside in the marrow and have the unique ability to give rise to all of the different mature blood cell types. The HSCs are self renewing cells: when they proliferate, at least some of their daughter cells remain as HSCs, so the pool of stem cells does not become depleted. The other daughters of HSCs, however can each commit to any of alternative differentiation pathways that lead to the production of one or more specific types of blood cells.
Umbilical cord blood from a newborn baby that can be collected from its placenta and umbilical cord after the cord has been clamped is rich in hematopoietic stem cells, and is utilized as a source of stem cells for transplantation. Umbilical cord blood up to 180mL of Blood from a newborn baby that is returned to the neonatal circulation if the Umbilical cord is not prematurely clamped
Lineages
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All blood cells are divided into three lineages.
- Erythroid cells are the oxygen carrying red blood cells. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood
- Lymphoid cells are the cornerstone of the adaptive immune system. The lymphatic system in Vertebrates is a network of conduits that carry a clear fluid called Lymph. They are derived from common lymphoid progenitors. The lymphoid lineage is primarily composed of T-cells and B-cells. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. B cells are Lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by (white blood cells)
- Myeloid cells, which includes granulocytes, megakaryocytes, and macrophages, are derived from common myeloid progenitors, and are involved in such diverse roles as innate immunity, adaptive immunity, and blood clotting. The term myeloid suggests an origin in the Bone marrow or Spinal cord, or a resemblance to the marrow or spinal cord Granulocytes are a category of White blood cells characterised by The megakaryocyte is a Bone marrow cell responsible for the production of blood Platelets necessary for normal blood Clotting Megakaryocytes normally Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Immune system|Adaptive immune systemThe innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms in a non-specific manner Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic Coagulation is a complex process by which Blood forms Clots It is an important part of Hemostasis (the cessation of blood loss from a damaged vessel whereby
Granulopoiesis
Granulopoiesis (or granulocytopoiesis) is hematopoiesis of granulocytes. Granulocytes are a category of White blood cells characterised by
It occurs primarily within bone marrow. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of
It involves the following stages:
- Pluripotential hemopoietic stem cell
- Myeloblast
- Promyelocyte
- Eosino/neutro/basophilic myelocyte
- Metamyelocyte
- Band cell (Stab cell)
- Granulocytes (Eosino/neutro/basophil)
Locations
In developing embryos, blood formation occurs in aggregates of blood cells in the yolk sac, called blood islands. Hematopoietic stem cells (HSCs are Stem cells that give rise to all the blood cell types including Myeloid ( Monocytes and Macrophages, Neutrophils The myeloblast is a unipotent stem cell which will differentiate into one of the actors of the Granular series A promyelocyte (or progranulocyte) is a Granulocyte precursor developing from the Myeloblast and developing into the Myelocyte. A myelocyte is a young cell of the granulocytic series occurring normally in Bone marrow, but not in circulating Blood (except when caused by A myelocyte is a young cell of the granulocytic series occurring normally in Bone marrow, but not in circulating Blood (except when caused by A myelocyte is a young cell of the granulocytic series occurring normally in Bone marrow, but not in circulating Blood (except when caused by A metamyelocyte is a cell undergoing Granulopoiesis, derived from a Myelocyte, and leading to a Band cell. A band cell (or band neutrophil) is a cell undergoing Granulopoiesis, derived from a Metamyelocyte, and leading to a mature Granulocyte. Granulocytes are a category of White blood cells characterised by Eosinophil granulocytes, usually called eosinophils (or less commonly acidophils) are White blood cells that are one of the Immune System components Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of White blood cells in humans and form an essential part of the A Blood island is an Angiogenic cluster of cells which develops from the posterior Mesoderm and is found the yolk sac of embryos As development progresses, blood formation occurs in the spleen, liver and lymph nodes. The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red The liver is a vital organ in the human body and is present in Vertebrates and some other animals A Lymph node ( lɪmf noʊd is an organ consisting of many types of cells and is a part of the Lymphatic system. When bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of However, maturation, activation, and some proliferation of lymphoid cells occurs in secondary lymphoid organs (spleen, thymus, and lymph nodes). In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum. In children, hematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, vertebrae, and sternum.
Extramedullary
In some cases, the liver, thymus, and spleen may resume their haematopoietic function, if necessary. This is called extramedullary haematopoiesis. It may cause these organs to increase in size substantially. [1]
Other vertebrates
In some vertebrates, haematopoiesis can occur wherever there is a loose stroma of connective tissue and slow blood supply, such as the gut, spleen, kidney or ovaries. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes The spleen is an organ found in all Vertebrate animals In humans the spleen is located in the abdomen of the body where it functions in the destruction of redundant Red The kidneys are complicated organs that have numerous biological roles "Ovaria" redirects here This is also a proposed section and a Synonym of Solanum.
Maturation
As a stem cell matures it undergoes changes in gene expression (the rate at which a gene is converted to its encoded products) that limit the cell types that it can become and move it closer to a specific cell type. These changes can often be tracked by monitoring the presence of proteins on the surface of the cell. Each successive change moves the cell closer to its final choice of cell type and further limits its potential cell type until it is fully differentiated. This process is usually presented as a dendrogram or decision tree, which starts with a stem cell at the single starting point, and branches for the major lineages that branch into intermediate semi-differentiated cell types, and eventually, to fully differentiated cells. A dendrogram (from Greek dendron "tree" -gramma "drawing" is a tree diagram frequently used to illustrate the arrangement
Determination
It seems like it's the location of blood cells that makes the cell determination and not vice versa (i. Cell fate determination is the programming of a cell to follow a specified path of Cell differentiation. e. e. g. that a hematopoietic stem cell determined to differentiate into a specific cell type would end up at a destined location). Hematopoietic stem cells (HSCs are Stem cells that give rise to all the blood cell types including Myeloid ( Monocytes and Macrophages, Neutrophils For instance, the thymus provides an environment for thymocytes to differentiate into a variety of different functional T cells. In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum.
For the stem cells and other undifferentiated blood cells in the bone marrow, the determination is generally explained by the determinism theory of hematopoiesis, saying that colony stimulating factors and other factors of the hematopoietic microenvironment determine the cells to follow a certain path of cell differentiation. This is the classical way of describing hematopoiesis. In fact, however, it is not really true. The ability of the bone marrow to regulate the quantity of different cell types to be produced is more accurately explained by a stochastic theory: Undifferentiated blood cells are determined to specific cell types by randomness. The hematopoietic microenvironment avails some of the cells to survive and some, on the other hand, to perform apoptosis. By regulating this balance between different cell types, the bone marrow can alter the quantity of different cells to ultimately be produced.
Haematopoietic growth factors
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Red and white blood cell production is regulated with great precision in healthy humans, and the production of granulocytes is rapidly increased during infection. Stem cell factor ( SCF) otherwise known as KIT ligand or Steel factor,is a Cytokine which binds CD117 (c-Kit Thrombopoietin (leukemia virus oncogene ligand megakaryocyte growth and development factor, also known as THPO, is a Glycoprotein Hormone produced Interleukins are a group of Cytokines (secreted Signaling molecules) that were first seen to be expressed by White blood cells ( Leukocytes hence Granulocyte-macrophage colony-stimulating factor, often abbreviated to GM-CSF, is a Protein secreted by Macrophages T cells Mast Erythropoietin (ɨˌɹɪθɹoʊˈpɔɪɨtɨn /ɨˌɹɪθɹoʊˈpɔɪtən/ or /ɨˌɹiːθɹoʊ-/ or EPO is a Glycoprotein Hormone that controls Macrophage colony-stimulating factor, or M-CSF is a secreted Cytokine which influences Hemopoietic stem cells to differentiate into Macrophages or other Granulocyte colony-stimulating factor ( G-CSF or GCSF) is a Colony-stimulating factor hormone SDF-1 ( Stromal cell -derived factor-1 is small Cytokine belonging to the Chemokine family that is officially designated Chemokine (C-X-C motif Tumor necrosis factor ( TNF, cachexin or cachectin and formally known as Tumor necrosis factor-alpha) is a Cytokine involved in systemic Transforming growth factor (sometimes referred to as Tumor growth factor, or TGF) is used to describe two classes of Polypeptide Growth factors The proliferation and self-renewal of these cells depend on stem cell factor (SCF). Glycoprotein growth factors regulate the proliferation and maturation of the cells that enter the blood from the marrow, and cause cells in one or more committed cell lines to proliferate and mature. Three more factors which stimulate the production of committed stem cells are called colony-stimulating factors (CSFs) and include granulocyte-macrophage CSF (GM-CSF), granulocyte CSF (G-CSF) and macrophage CSF (M-CSF). Colony-stimulating factors (CSFs are secreted Glycoproteins which bind to receptor proteins on the surfaces of Hemopoietic stem cells and thereby activate Intracellular Granulocyte-macrophage colony-stimulating factor, often abbreviated to GM-CSF, is a Protein secreted by Macrophages T cells Mast Granulocyte colony-stimulating factor ( G-CSF or GCSF) is a Colony-stimulating factor hormone Macrophage colony-stimulating factor, or M-CSF is a secreted Cytokine which influences Hemopoietic stem cells to differentiate into Macrophages or other These stimulate a lot of granulocyte formation. Granulocytes are a category of White blood cells characterised by They are active on either progenitor cells or end product cells. The concept of a progenitor cell is difficult to define Like Stem cells, progenitor cells have a capacity to differentiate into a specific type of cell
Erythropoietin is required for a myeloid progenitor cell to become an erythrocyte. Erythropoietin (ɨˌɹɪθɹoʊˈpɔɪɨtɨn /ɨˌɹɪθɹoʊˈpɔɪtən/ or /ɨˌɹiːθɹoʊ-/ or EPO is a Glycoprotein Hormone that controls [2] On the other hand, thrombopoietin makes myeloid progenitor cells differentiate to megakaryocytes (thrombocyte-forming cells). Thrombopoietin (leukemia virus oncogene ligand megakaryocyte growth and development factor, also known as THPO, is a Glycoprotein Hormone produced The megakaryocyte is a Bone marrow cell responsible for the production of blood Platelets necessary for normal blood Clotting Megakaryocytes normally Thrombocytes are cells that play a key role in blood clotting [2] Examples of cytokines and the blood cells they give rise to, is shown in the picture to the right.
Transcription factors
Growth factors initiate signal transduction pathways, altering transcription factors, that, in turn activate genes that determines the differentiation of blood cells. In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences
The early committed progenitors express low levels of transcription factors that may commit them to discrete cell lineages. Which cell lineage is selected for differentiation may depend both on chance and on the external signals received by progenitor cells. Several transcription factors have been isolated that regulate differentiation along the major cell lineages. For instance, PU. 1 commits cells to the myeloid lineage whereas GATA-1 has an essential role in erythropoietic and megakaryocytic differentiation.
References
- Parslow,T G. ;Stites, DP. ; Terr, AI. ; and Imboden JB. Medical Immunology. 1. ISBN 0838562787
External links
- granulopoiesis at eMedicine Dictionary
- -1838481350 at GPnotebook
- Overview at tulane.edu
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