All About the Female Reproductive System

7. Blastocyst: The Formation of the Embryo

The formation of the embryo starts inside a complex cell called a blastocyst, which consists of two groups of inner and outer cells combined with fluids. This blastocyst is surrounded and protected by a thick membrane called a zona pellucida. The cells that will become the fetal placenta are located just below this membrane and will provide future nourishment for the embryo. The inner cells of the blastocyst become the bones, tissues, and the organs of the fetus. A few days after fertilization, the cells inside the blastocyst begin to develop quickly, producing specialized cells the human body requires. The blastocyst breaks through the zona pellucida and travels through the fallopian tubes to the uterus.

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