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## Human Reproduction ### Blastocyst Formation The blastocyst is formed from the morula, which is made up of blastomeres. The blastomeres are arranged into an outer layer called **trophoblast** and an inner cell mass, attached to the trophoblast. The trophoblast attaches to the endometrium, and th...

## Human Reproduction ### Blastocyst Formation The blastocyst is formed from the morula, which is made up of blastomeres. The blastomeres are arranged into an outer layer called **trophoblast** and an inner cell mass, attached to the trophoblast. The trophoblast attaches to the endometrium, and the inner cell mass differentiates to form the embryo. This process is called **implantation** and leads to pregnancy. ### Pregnancy and Embryonic Development During pregnancy, finger-like projections called **chorionic villi** grow from the trophoblast, surrounded by uterine tissue and maternal blood. The chorionic villi and uterine tissue form a unit called the **placenta**, which allows for the exchange of nutrients and waste between the mother and the embryo. The placenta is connected to the embryo via the **umbilical cord**. The placenta also produces hormones including: * **Human chorionic gonadotropin (hCG)** * **Human placental lactogen (hPL)** * **Estrogens** * **Progestogens** A hormone called **relaxin**, produced by the ovary, also plays a role in pregnancy. **Other Hormones:** The levels of other hormones including: * **Estrogens** * **Progestogens** * **Cortisol** * **Prolactin** * **Thyroxine** Are increased several-folds in the maternal blood. These hormones are essential for supporting fetal growth and the metabolic changes in the mother. ### Embryonic Development After implantation, the inner cell mass differentiates to form the embryo.