{{Short description|Tissue of bone marrow}} {{About|bone marrow cells and tissue|spinal cord tissue|spinal cord}}
thumb|400px|Diagram showing the development of different blood cells from haematopoietic stem cell to mature cells thumb|400px|Comprehensive diagram that shows the development of different blood cells from haematopoietic stem cell to mature cells in both myeloid and lymphoid lineages.
'''Myeloid tissue''', in the bone marrow sense of the word ''myeloid'' (''myelo-'' + ''-oid''), is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and '''myelogenous tissue''' (''myelo-'' + ''-genous'') is any tissue of, or arising from, bone marrow; in these senses the terms are usually used synonymously, as for example with chronic myeloid/myelogenous leukemia.
In hematopoiesis, '''myeloid cells''', or myelogenous cells are blood cells that arise from a progenitor cell for granulocytes, monocytes, erythrocytes, or platelets<ref name="pmid15147715">{{cite journal | vauthors=Kawamoto H, Minato N | title=Myeloid cells | journal= The International Journal of Biochemistry & Cell Biology | volume=36 | issue=8 | year=2004 | pages=1374–1379 | pmid=15147715 | doi=10.1016/j.biocel.2004.01.020}}</ref><ref name="pmid18295580">{{cite journal |vauthors=Orkin SH, Zon LI | title=Hematopoiesis: an evolving paradigm for stem cell biology | journal= Cell | volume=132| issue=4 | year=2008 | pages=631–644 | url= | doi=10.1016/j.cell.2008.01.025 | pmc=2628169 | pmid=18295580}}</ref> (the common myeloid progenitor, that is, CMP or CFU-GEMM), or in a narrower sense also often used, specifically from the lineage of the myeloblast (the myelocytes, monocytes, and their daughter types). Thus, although all blood cells, even lymphocytes, are normally born in the bone marrow in adults, myeloid cells in the narrowest sense of the term can be distinguished from lymphoid cells, that is, lymphocytes, which come from common lymphoid progenitor cells that give rise to B cells and T cells.<ref name="pmid18295580" /> Those cells' differentiation (that is, lymphopoiesis) is not complete until they migrate to lymphatic organs such as the spleen and thymus for programming by antigen challenge. Thus, among leukocytes, the term ''myeloid'' is associated with the innate immune system, in contrast to ''lymphoid'', which is associated with the adaptive immune system. Similarly, ''myelogenous'' usually refers to nonlymphocytic white blood cells,<ref>{{cite web | title = Definition of Myelogenous | publisher = MedicineNet | date = August 28, 2013 | url = http://www.medicinenet.com/script/main/art.asp?articlekey=4481 | access-date = 2015-09-10 }}</ref> and ''erythroid'' can often be used to distinguish "erythrocyte-related" from that sense of ''myeloid'' and from ''lymphoid''.<ref name="pmid22345399">{{cite journal |vauthors=Yuan J, Nguyen CK, Liu X, Kanellopoulou C, Muljo SA | title=Lin28b reprograms adult bone marrow hematopoietic progenitors to mediate fetal-like lymphopoiesis | journal= Science | volume=335 | issue=6073 | year=2012 | pages=1195–1200| doi=10.1126/science.1216557 | pmc=3471381 | pmid=22345399| bibcode=2012Sci...335.1195Y }}</ref>
The word ''myelopoiesis'' has several senses in a way that parallels those of ''myeloid'', and myelopoiesis in the narrower sense is the regulated formation specifically of myeloid leukocytes (myelocytes), allowing that sense of ''myelopoiesis'' to be contradistinguished from erythropoiesis and lymphopoiesis (even though all blood cells are normally produced in the marrow in adults).
Myeloid neoplasms always concern bone marrow cell lineage and are related to hematopoietic cells. Myeloid tissue can also be present in the liver and spleen<ref name=T4>Semester 4 medical lectures at Uppsala University 2008 by Leif Jansson</ref> in fetuses, and sometimes even in adults as well, which leads to extramedullary hematopoiesis.
There is one other sense of ''myeloid'' that means "pertaining to the spinal cord", but it is much less commonly used. ''Myeloid'' should not be confused with ''myelin'', referring to an insulating layer covering the axons of many neurons.
==See also== * Acute myeloid leukemia * Chronic myelogenous leukemia * Hematopoietic stem cell * Lymphocyte * Myelocyte
==References== {{reflist}}
==External links== {{Commons category|Myeloid cells}} {{Wiktionary|myeloid}}
{{Osseous and chondromatous tumors}} {{System and organs}} {{Myeloid blood cells and plasma}}
Category:Blood cells Category:Tissues (biology)