The term refers to the pathways or tracks of blood cell development, beginning with what’s known as ahematopoietic stem cell(HSC), going through a series of steps to arrive at the final product—a mature blood cell, whether it’s a red blood cell, a white blood cell such as a lymphocyte, or some other type of blood cell. Other terms for this process of blood cell formation include hematogenesis, hemogenesis, and hemopoiesis.
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What Is Hematopoietic?
You might come across the word hematopoiesis, or the adjective hematopoietic, in a number of different scenarios:
Overview
Circulating blood contains a mix of cells, cell products, and fluids. Our bodies produce blood cells continuously from the time we are in the womb up to old age. Millions of blood cells are replaced each day as they live out their lifespans. Different types of cells have different lifespans, and in healthy adults, red blood cells normally live about 100 to 120 days before they need to be replaced.
There are more than 10 different kinds of blood cells, each performing its own set of tasks. Though red and white blood cells may end up in different places in the body, production starts in the bone marrow.
In the Bone Marrow
Within the hollows of certain bones, the marrow tissue exists, including hematopoieticstem cells(also called pluripotent hematopoietic stem cells) that give rise to all of the different types of blood cells. Some of these stem cells remain “uncommitted” so that they can continue to reproduce cells of whatever type is needed, sort of like a queen bee laying eggs, but other stem cells start the process of committing, to become “progenitors” or “precursors” of distinctly different cell lines. Cell lines/lineages can be thought of as different branches of the blood cell family tree.
Blood-forming cells make for two different sides of the family tree:
In the Blood, Fluids, and Tissues
Once grown and mature, red blood cells stay in the blood. White blood cells may also be found in the bloodstream, but they may be more prevalent at other sites. For instance, lymphocytes are far more common and numerous inthe lymphatic systemthan in the blood.
From Bone Marrow to Bloodstream
If the HSC commits to producing mature blood cells, it will undergo several cell divisions before becoming that cell. Every time the cell divides, it takes on more of the characteristics of the adult cell it will become. In other words, it becomes more differentiated or specialized.
Stimulating the body to produce more new blood cells—a sort of artificial hematopoiesis–can be helpful in certain situations. For instance, sometimes the bone marrow is stimulated in advance of a planned cancer therapy when profound suppression of the blood-forming cells in the marrow is expected.
When Hematopoietic Cells Go Astray
Like any cell, the HSCs can undergo a mutation that leads to dysfunctional or malignant cells being produced rather than healthy cells. Depending on what stage of differentiation the cell is in when it makes this transformation, it gives rise to different types of disorders: myeloproliferative disorders, leukemias, lymphomas, and myelomas.
An abnormal younger cell type may be referred to as a ‘blast.’ Blasts in patients with leukemia can suggest the cancerous transformation occurred in a blood-forming cell that was at an earlier stage of development. If the predominant cells in leukemia or lymphoma are more mature types, this indicates the cancerous transformation happened to a more mature cell or a cell that was closer to the final adult stage.
In lymphoma, there can be different lymphomas that reflect all different stages of lymphocyte development, including the developmental paths for B-cells and T-cells; thus, there are B-cell lymphomas, T-cell lymphomas, and even natural killer T-cell lymphomas.
Hematopoietic Cell Transplantation - Bone Marrow Transplants
The treatment of leukemia, lymphoma and other blood cancers may involve a transplant of hematopoietic stem cells. These can be your own cells, harvested from your bone marrow (autologous), or from a donor (allogeneic).Techniques used to obtain healthy blood-forming cells from the donorvary, but the transplant itself is a simple transfusion as the hematopoietic stem cells migrate from the blood into the bone marrow.
Extramedullary Hematopoiesis
This is the term used for blood cell production that occurs outside of the bone marrow. It can be seen in chronic anemia, with the production of blood cells in the liver, spleen and sometimes in the lymph nodes. In other scenarios, there may be malignant hematopoietic cells located in areas outside of the bone marrow.
2 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kim CH.Homeostatic and pathogenic extramedullary hematopoiesis.J Blood Med. 2010;1:13–19. doi:10.2147/JBM.S7224Weiskopf K, Schnorr PJ, Pang WW, et al.Myeloid Cell Origins, Differentiation, and Clinical Implications.Microbiol Spectr. 2016;4(5):10.1128/microbiolspec.MCHD-0031-2016. doi:10.1128/microbiolspec.MCHD-0031-2016
2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kim CH.Homeostatic and pathogenic extramedullary hematopoiesis.J Blood Med. 2010;1:13–19. doi:10.2147/JBM.S7224Weiskopf K, Schnorr PJ, Pang WW, et al.Myeloid Cell Origins, Differentiation, and Clinical Implications.Microbiol Spectr. 2016;4(5):10.1128/microbiolspec.MCHD-0031-2016. doi:10.1128/microbiolspec.MCHD-0031-2016
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Kim CH.Homeostatic and pathogenic extramedullary hematopoiesis.J Blood Med. 2010;1:13–19. doi:10.2147/JBM.S7224Weiskopf K, Schnorr PJ, Pang WW, et al.Myeloid Cell Origins, Differentiation, and Clinical Implications.Microbiol Spectr. 2016;4(5):10.1128/microbiolspec.MCHD-0031-2016. doi:10.1128/microbiolspec.MCHD-0031-2016
Kim CH.Homeostatic and pathogenic extramedullary hematopoiesis.J Blood Med. 2010;1:13–19. doi:10.2147/JBM.S7224
Weiskopf K, Schnorr PJ, Pang WW, et al.Myeloid Cell Origins, Differentiation, and Clinical Implications.Microbiol Spectr. 2016;4(5):10.1128/microbiolspec.MCHD-0031-2016. doi:10.1128/microbiolspec.MCHD-0031-2016
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