193
The Placenta and
Umbilical Cord
Chapter 19
Chelsea Ward, MD
DEVELOPMENT
❍ What cell is the precursor of the placenta?
Trophoblast.
❍ At what stage, does the trophoblast develop?
Blastocyst—8 days.
❍ When does implantation occur?
6 to 12 days postfertilization.
❍ What two cell types arise from the trophoblast?
Syncytiotrophoblast and cytotrophoblast.
❍ What is the role of the cytotrophoblast?
Form chorionic plate and chorion leave, invade and replace spiral arteries with uteroplacental arteries.
❍ What is the role of the syncytiotrophoblast?
Transport of gases, nutrients, and waste products; synthesis of peptide and steroid hormones.
❍ What are the three distinct layers of the fetal membranes?
Amnion, chorion laeve, and decidua capsularis.
❍ What placental hormone functions to maintain the corpus luteum in early pregnancy?
human chorionic gonadotropin (hCG).
❍ When does the hCG level peak?
9 to 10 weeks’ gestation.