Embryotroph is the embryonic nourishment in placental animals.

Formation of syncytiotrophoblast

On approximately the seventh day of development, the

trophoblast The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the pl ...

(cells that make up the outer part of the

blastocyst The blastocyst is a structure formed in the early embryonic development of mammals. It possesses an inner cell mass (ICM) also known as the ''embryoblast'' which subsequently forms the embryo, and an outer layer of trophoblast cells called the t ...

) divides to form two separate layers: an inner

cytotrophoblast "Cytotrophoblast" is the name given to both the inner layer of the trophoblast (also called layer of Langhans) or the cells that live there. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo ...

layer, and an outer

syncytiotrophoblast Syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'- "of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nut ...

layer. Using enzymes, the syncytiotrophoblast penetrates the tissues of the mother, then it attaches to these tissues by burrowing with long projections, breaking maternal blood vessels. The chemical reason why this process occurs is currently unknown.

Uterine milk

Uterine milk Uterine glands or endometrial glands are tubular glands, lined by ciliated columnar epithelium, found in the functional layer of the endometrium that lines the uterus. Their appearance varies during the menstrual cycle. During the proliferative ph ...

is part of the embryotroph. It is a white secretion containing proteins and amino acids that nourishes the embryo during development. The uterine milk is the actual nutritional liquid that feeds the embryo, while the embryotroph is the uterine milk plus the syncytiotrophoblast.

Malformations and embryotrophic nutrition

Studies have shown that when embryotrophic nutrition is interrupted for some reason or another, malformations in embryos tend to occur. This is expected, because when important proteins and amino acids are withheld, the embryo will surely be at a disadvantage. The

yolk sac The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is far ...

is the part of the embryo most likely to be malformed, leading to other malformations later on. Laboratory Animals, "Methods for the Study of Embryotrophic Nutrition"
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References

{{Embryology, date=November 2012 Embryology