extraembryonic blastoderm

ex·tra·em·bry·on·ic blas·to·derm

the part of the blastoderm that is not incorporated in the embryo but forms membranes concerned in its nourishment and protection.

extraembryonic blastoderm

[-em′brē·on′ik]
Etymology: L, extra + Gk, en, in, bryein, to grow
the area of the blastoderm outside the embryo that gives rise to the membranes that surround the embryo during gestation. Compare embryonic blastoderm. See also allantois, amnion, chorion, yolk sac.