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Embryonic Structures

The anatomical parts that make up an organism in the early stages of development.

Year introduced: 1998


Embryo, Nonmammalian

The developmental entity of a fertilized egg (ZYGOTE) in animal species other than MAMMALS. For chickens, use CHICK EMBRYO.

Year introduced: 1975


Aborted Fetus

A mammalian fetus expelled by INDUCED ABORTION or SPONTANEOUS ABORTION.

Year introduced: 2003



The encapsulated embryos of flowering plants. They are used as is or for animal feed because of the high content of concentrated nutrients like starches, proteins, and fats. Rapeseed, cottonseed, and sunflower seed are also produced for the oils (fats) they yield.

Year introduced: 1963


Embryo, Mammalian

The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.

Year introduced: 2008 (1963)


Chick Embryo

The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.

Year introduced: 1964



A post-MORULA preimplantation mammalian embryo that develops from a 32-cell stage into a fluid-filled hollow ball of over a hundred cells. A blastocyst has two distinctive tissues. The outer layer of trophoblasts gives rise to extra-embryonic tissues. The inner cell mass gives rise to the embryonic disc and eventual embryo proper.

Year introduced: 1974


Rhox5 protein, rat [Supplementary Concept]

RefSeq NM_022175

Date introduced: September 29, 2004


Pem protein, mouse [Supplementary Concept]

localized to the X chromosome; expressed in extraembryonic tissues during early development; member of the homeobox gene family; RefSeq NM_008818

Date introduced: December 21, 1994

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