proamnion


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pro·am·ni·on

(prō-am'nē-on),
An area of the extraembryonic membranes beneath, and in front of, the developing head of a young embryo that remains without mesoderm for some time.

proamnion

(prō-ăm′nē-ŏn) [Gr. pro, before, + amnion, amnion]
A region anterior to the head in a vertebrate embryo in which mesoderm is lacking.