proamnionn.
/prəʊˈamnɪən/, U.S. /proʊˈæmniˌɑn/, /proʊˈæmniən/ Embryology.
In many vertebrate embryos: an area of blastoderm, located at the cephalic end, in which there is no mesoderm separating the ectoderm and endoderm.
ΚΠ
1887 Amer. Naturalist 21 396 There is found a proamnion not only in Rodents, Bats, and Marsupials, but also in Carnivora and Insectivora.
1931 Q. Rev. Biol. 6 23/1 Primordial germ cells were first seen in the embryo during the primitive streak stage at the outer edge of the proamnion anterior and antero-lateral to the head fold.
1979 Nature 9 Aug. 499/1 Between the mesoderm and the anterior boundary of the area pellucida is the proamnion, which is without mesoderm.
1998 Philos. Trans. (Royal Soc.) B. 353 1105/1 A small, extra-embryonic proamnion..immediately abuts and surrounds the rostral extremity of the head process.
This entry has been updated (OED Third Edition, June 2007; most recently modified version published online March 2022).
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