- Inner cell mass
Name = PAGENAME
GraySubject = 6
GrayPage = 46
Caption = Blastocyst with an
inner cell massand trophoblast.
CarnegieStage = 3
Days = 6
DorlandsPre = m_04
DorlandsSuf = 12515766
embryogenesisof most eutherianmammals, the inner cell mass (abbreviated ICM and also known as the embryoblast or pluriblast(the latter term being applicable to all mammals)) is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus. This structure forms in the earliest steps of development, before implantationinto the endometriumof the uterushas occurred. The ICM lies within the blastocoele(more correctly termed "blastocyst cavity", as it is not strictly homologous to the blastocoele of anamniote vertebrates) and is entirely surrounded by the single layer of cells called trophoblast.
The ICM differentiates into two types of cells,
Only the cells of the epiblast give rise to cells inside the embryo, while hypoblast cells form only extraembryonic tissue (
extraembryonic endoderm). All three germ layersof the definitive embryo, as well as extraembryonic mesoderm, arise from the epiblast.
It is the source of early
stem cells. [cite web |url=http://www.kumc.edu/stemcell/early.html |title=Stem Cell Research Basics: Early Stem Cells |accessdate=2007-10-11 |format= |work=]
It can form all tissues except
trophoblast. [cite web |url=http://cancerweb.ncl.ac.uk/cgi-bin/omd?inner+cell+mass |title=Definition: inner cell mass from Online Medical Dictionary |accessdate=2007-10-11 |format= |work=]
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