During mammalian embryogenesis, the first differentiation event that occurs leads

the entire embryo

Explanation:

The trophectoderm refers to the polarized single cell layer that forms the wall of the blastocyst, thereby forming the first epithelium during embryogenesis. Moreover, the blastocyst is composed of 1-an inner cell mass (ICM) which will form all the tissues of the embryo's body, and 2-an outer layer composed of cells collectively called the trophoblast. The ICM of the blastocyst will form the embryoblast (which subsequently will give rise to the embryo itself) and the fetus, while the trophoblast will form all of the supporting tissues (i.e., amniotic sac, placenta, and umbilical cord). In humans, the blastocyst is the developmental stage of the embryo on day 5 after fertilization.

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Explanation:

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