Placenta

Anatomy and Development

The placenta is a temporary organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. It is formed from the same sperm and egg cells that form the fetus and is expelled from the organism after birth, a process known as the "afterbirth".1(https://www.ncbi.nlm.nih.gov/books/NBK279512/)

The development of the placenta begins in the first weeks of embryonic development, following fertilization. The blastocyst, the early stage embryo, implants itself into the wall of the uterus. The outer layer of the blastocyst, known as the trophoblast, differentiates into two layers: the cytotrophoblast and the syncytiotrophoblast. The syncytiotrophoblast invades the maternal endometrium, the lining of the uterus, and establishes contact with maternal blood vessels. This forms the basis of the placenta.2(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Functions

The placenta performs several critical functions during pregnancy. It serves as a conduit for the exchange of nutrients, gases, and wastes between the mother and the fetus. It also produces hormones that support pregnancy and fetal development, and it acts as a barrier to protect the fetus from the maternal immune system and potential pathogens.3(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Nutrient and Gas Exchange

The placenta facilitates the transfer of nutrients and oxygen from the mother's blood to the fetus. This is achieved through a network of blood vessels that connect to the umbilical cord, which attaches the fetus to the placenta. The placenta also removes waste products, such as carbon dioxide, from the fetal blood for elimination by the mother's body.4(https://www.ncbi.nlm.nih.gov/books/NBK279512/)

Hormone Production

The placenta produces several hormones that are essential for maintaining pregnancy and supporting fetal development. These include human chorionic gonadotropin (hCG), progesterone, and estrogen. hCG signals the ovaries to maintain the production of progesterone, which is necessary to prevent the shedding of the endometrium. Progesterone and estrogen also promote the growth of the uterus and prepare the mother's body for breastfeeding.5(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Immune Barrier

The placenta acts as an immune barrier between the mother and the fetus, protecting the fetus from the maternal immune system and potential pathogens. The placenta expresses immune-modulatory molecules that prevent maternal immune cells from recognizing and attacking fetal tissues. It also limits the transmission of pathogens from the mother to the fetus by expressing pathogen recognition receptors and secreting antimicrobial peptides.6(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Pathology

Placental dysfunction can lead to a variety of pregnancy complications, including preeclampsia, intrauterine growth restriction, and preterm birth. These conditions can have serious consequences for both the mother and the fetus.7(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Preeclampsia

Preeclampsia is a condition characterized by high blood pressure and damage to another organ system, often the liver and kidneys, in pregnant women. It is thought to be caused by poor placental development and function, leading to reduced blood flow to the placenta. This can result in poor fetal growth and premature birth.8(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) is a condition where a fetus is smaller than expected for the number of weeks of pregnancy. It is often caused by problems with the placenta, such as poor blood flow or infection, which prevent the fetus from receiving adequate nutrients and oxygen.9(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

Preterm Birth

Preterm birth, defined as birth before 37 weeks of gestation, can be caused by placental dysfunction. Conditions such as preeclampsia and IUGR can lead to preterm birth as they may necessitate early delivery to protect the health of the mother and the fetus.10(https://www.ncbi.nlm.nih.gov/books/NBK532983/)

References

1. "Placenta: Anatomy and Functions". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK279512/ 2. "Development of the Placenta". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 3. "Functions of the Placenta". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 4. "Nutrient and Gas Exchange". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK279512/ 5. "Hormone Production by the Placenta". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 6. "The Placenta as an Immune Barrier". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 7. "Pathology of the Placenta". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 8. "Preeclampsia". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 9. "Intrauterine Growth Restriction". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/ 10. "Preterm Birth". NCBI Bookshelf. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532983/