Membranous structure in amniotes, within which the embryo and fetus develop.
Note: It consists of a thin but tough, transparent pair of membranes, the
amnion and
chorion, that hold the developing embryo (and later
fetus) until shortly before
birth.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 721 (https://doi.org/10.1515/pac-2015-1202)