Trophectoderm (TE) Medically Reviewed

Last Updated: April 16, 2020

Definition - What does Trophectoderm (TE) mean?

The trophectoderm is a layer of cells on the outer edge of a blastocyst. These cells provide nutrients for the developing embryo, facilitate implantation into the uterine lining and become part of the placenta.

The trophectoderm begins to form around the 5th day after an egg is fertilized, at the same time as the rest of the blastocyst.

The trophectoderm can also be called the trophoblast or T cells.

FertilitySmarts explains Trophectoderm (TE)

The trophectoderm is responsible for providing food and chemical messages to the developing embryo. In addition to nourishing the cells of the embryo, it protects the inner cell mass (ICM) from the outside environment. The cells that make up the trophectoderm are the only cells of the embryo that contact the uterine wall.

The blastocyst implants in the uterine wall when the cells of the trophectoderm nearest to the inner cell mass (ICM) touch and adhere to the uterine lining. On contact, the cells of the trophectoderm begin to divide rapidly, causing it to become several layers thick.

The trophectoderm does not become part of the fetus but does become some of the supporting structures, such as the placenta.

Pre-Implantation Genetic Testing (PGT)

When in vitro fertilization (IVF) and Pre-Implantation Genetic Testing (PGT) is used, a trophectoderm biopsy may be performed to examine the DNA of the embryos to determine if an embryo transfer should take place.

In this procedure, some of the cells of the trophectoderm are removed, the rest of the embryo is frozen and the cells are sent to a genetic laboratory where its chromosome number or karyotypes are tested. This can provide information on the genes of the developing embryos so that only a balanced or normal embryo is transferred.

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  • Martini F, et al. Human Anatomy. (2003).
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