Trophectoderm (TE)

Definition - What does Trophectoderm (TE) mean?

The trophectoderm is a layer of cells on the outer edge of a blastocyst. The trophectoderm begins to form on the 5th day after an egg is fertilized, at the same time as the rest of the blastocyst. These cells provide nutrients for the developing embryo and will later become the placenta.

The trophectoderm is also called the trophoblast or T cells.

FertilitySmarts explains Trophectoderm (TE)

The trophectoderm is responsible for providing food 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 pre-embryo that contact the uterine wall.

The blastocyst implants in the uterine wall when the cells of the trophectoderm nearest to the 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.

With in vitro fertilization (IVF), a trophectoderm biopsy may be performed to examine the DNA of the blastocyst before it is implanted. In this procedure, some of the cells of the trophectoderm are removed and its chromosomes are tested. This can provide information on the developing embryo's genes so that only a healthy embryo is implanted.

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