25 Placental Development
The placenta is a key organ which forms during childbirth to supply the fetus with oxygen and nutrients while disposing of carbon dioxide and other cellular waste products. The placenta connects directly to the umbilical cord to connect the mother’s circulation to the fetus’s.
Placental Development:
The diagram below depicts the formation of the placenta:
| Time frame | Major events |
| Day 0 (fertilization) | The union of sperm and egg forming the zygote |
| Day 5-7 (blastocyst formation) | Following fertilization, human chorionic gonadotropin (hCG) prevents menstruation and breakdown of the endometrium. The blastocyst (a cluster of cells derived from the fertilized egg) then implants into the uterine lining around days 5-7. The blastocyst starts to develop the trophoblast which eventually forms the placenta. |
| Day 6-7 (implantation) | The blastocyst reaches the uterus and begins the process of implantation by attaching to the endometrial lining. This trophoblasts continues to invade the uterine wall and forms two key components: The cytotrophoblast and the syncytiotrophoblast. |
| Day 8-12 (formation of chorionic villi) | The syncytiotrophoblast invades deeper into the uterine wall, where chorionic villi, small finger like projections develop to interact with the maternal blood supply |
Placenta function:
The placenta as depicted above acts as a biological interface between the mother and fetus, transporting essential nutrients (glucose and amino acids) to the fetus and transporting waste products back.
However, the placenta also produces hormones like hCG, estrogen and placenta to help sustain the pregnancy and regulate fetal development.
Here are some major placental hormones and their functions:
| Hormone | Function |
| Estrogen |
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| Progesterone |
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| hCG |
|