Erythropoiesis is the process by which
red blood cells (erythrocytes) are produced. In humanadults, this usually occurs within the bone marrow. In the early fetus, erythropoiesis takes place in the mesodermal cells of the yolk sac. By the third or fourth month, erythropoiesis moves to the spleen and liver. In humans with certain diseases and in some animals, erythropoiesis also occurs outside the bone marrow, within the spleenor liver. This is termed "extramedullary erythropoiesis".
tibiaand femurcease to be important sites of hematopoiesisby about age 25; the vertebrae, sternum, pelvisand ribs, and cranium bones continue to produce red blood cells throughout life.
In the process of red blood cell maturation, a cell undergoes a series of "differentiations". The following stages of development all occur within the
# pluripotent hematopoietic
# multipotent stem cell
# unipotent stem cell
basophilic normoblast/early normoblast
polychromatophilic normoblast/intermediate normoblast
orthochromatic normoblast/late normoblast
After these stages, the cell is released from the bone marrow, and ultimately becomes an "erythrocyte" or mature red blood cell circulating in the peripheral blood.
These stages correspond to specific appearances of the cell when stained with
Wright's stainand examined by light microscopy, but correspond to other biochemical changes.
In the process of maturation a basophilic pronormoblast is converted from a cell with a large nucleus and a volume of 900 µm3 to an enucleated disc with a volume of 95 µm3. By the reticulocyte stage, the cell has extruded its nucleus, but is still capable of producing hemoglobin.
Charactersitics seen in erythrocytes during erythropoesis
the following characteristics can be seen changing in the erythrocytes when they are maturing1. they show a reduction in the cell size.2. the cytoplasmic matrix increases in amount.3.staining reaction of the cytoplasm changes from basophilic to acidophilic. this is because of the decrease in the amount of RNA.4. initially the nucleus was large in size and contained open chromatin. but with the maturation of RBC's the size of the nucleus decreases and finally dissapears with the condensation of the chromatin material.
source:textbook of physiology by Dr. A.K.Jain reprint 2006-2007 3rd edition.
Regulation of erythropoiesis
A feedback loop involving
erythropoietinhelps regulate the process of erythropoiesis so that, in non-disease states, the production of red blood cells is equal to the destruction of red blood cells and the red blood cell number is sufficient to sustain adequate tissue oxygen levels but not so high as to cause sludging, thrombosis, or stroke. Erythropoietin is produced in the kidney and liver in response to low oxygen levels. In addition, erythropoietin is bound by circulating red blood cells; low circulating numbers lead to a relatively high level of unbound erythropoietin, which stimulates production in the bone marrow.
Recent studies have also shown that the peptide hormone
hepcidinmay play a role in the regulation of hemoglobin production, and thus effect erythropoiesis. The liver produces hepcidin. Hepcidin controls iron absorption in the gastrointestinal tract and iron release from reticuloendothelial tissue. Iron must be released from macrophagesin the bone marrow to be incorporated into the heme group of hemoglobinin erythrocytes.There are colony forming units that the cells follow during their formation. These cells are referred to as the committed cells including the granulocyte monocyte colony forming units
Also, loss of function of the erythropoietin receptor or JAK2 in mice cells causes failure in erythropoiesis, so production of red blood cells in embryos and growth is disrupted.
Also, if there is no feedback inhibition, such as SOCS (Suppressors of Cytokine Signaling) proteins in the system, that would cause giantism in mice.
Anemia: a condition with an abnormally low level of functional haemoglobin
Polycythemia: a condition with an abnormally high level of red blood cells
Source1. Nicolas, Gaul et al. (2002) Severe Iron Deficiency Anemia in Transgenic Mice Expressing Liver Hepcidin. Proceedings of the National Academy of Sciences of the United States of America. 99:7, 4596-4601
* [http://www.healthsystem.virginia.edu/internet/hematology/HessIDB/home.cfm Microscopic Hematology]
changes during erythropoiesis
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Look at other dictionaries:
erythropoiesis — [e rith΄rō poi ē′sis] n. [ModL < ERYTHRO + Gr poiēsis, a making: see POESY] the body process of developing red blood cells erythropoietic [e rith΄rōpoi et′ik] adj … English World dictionary
erythropoiesis — noun Etymology: New Latin Date: 1918 the production of red blood cells (as from the bone marrow) • erythropoietic adjective … New Collegiate Dictionary
erythropoiesis — Process of production of erythrocytes in the marrow in adult mammals. A pluripotent stem cell (CFU) produces, by a series of divisions, committed stem cells (BFU Es) that give rise to CFU Es, cells that will divide only a few more times to… … Dictionary of molecular biology
erythropoiesis — erythropoietic /i rith roh poy et ik/, adj. /i rith roh poy ee sis/, n. the production of red blood cells. [1915 20; ERYTHRO(CYTE) + POIESIS] * * * … Universalium
erythropoiesis — noun The production of red blood cells in bone marrow. See Also: erythropoietic … Wiktionary
erythropoiesis — The formation of red blood cells. SYN: erythrocytopoiesis. [erythrocyte + G. poiesis, a making] * * * eryth·ro·poi·e·sis i .rith rō pȯi ē səs n, pl e·ses .sēz the production of red blood cells (as from the bone marrow) called also … Medical dictionary
erythropoiesis — n. formation of red blood cells … English contemporary dictionary
erythropoiesis — [ɪˌrɪθrə(ʊ)pɔɪ i:sɪs] noun Physiology the production of red blood cells. Derivatives erythropoietic adjective … English new terms dictionary
erythropoiesis — eryth·ro·poi·e·sis … English syllables
erythropoiesis — n. the process of red blood cell (erythrocyte) production, which normally occurs in the blood forming tissue of the bone marrow. The ultimate precursor of the red cell is the haemopoietic stem cell, but the earliest precursor that can be… … The new mediacal dictionary