placento

Placento, or placenta in English, is a temporary organ that forms during pregnancy to connect the developing fetus to the uterine wall. It facilitates the exchange of gases, nutrients, and wastes between mother and fetus and synthesizes hormones that support pregnancy.

Development and structure: It begins to form after implantation from fetal trophoblast and maternal decidua basalis. The fetal portion, the chorion, develops chorionic villi; the maternal portion forms the decidua basalis. The placenta spans the uterine wall, presenting a fetal surface (chorionic plate) and a maternal surface (basal plate) with intervillous spaces filled with maternal blood. The fetal blood in the villi does not mix directly with maternal blood; exchange occurs across the placental barrier via diffusion, active transport, and vesicular mechanisms. The umbilical cord, containing two arteries and one vein, connects the fetus to the placental area.

Function: In addition to nutrition and respiration, the placenta secretes hormones such as human chorionic gonadotropin (hCG), progesterone, estrogens, and human placental lactogen, supporting corpus luteum function early on and regulating maternal physiology. It also participates in immune modulation to tolerate the fetus and provides limited barrier protection against some infections.

Clinical notes: Placental abnormalities include placenta previa, placenta accreta spectrum, and placental abruption, which can impact pregnancy outcomes. Placental development and function can be affected by maternal conditions such as hypertension, diabetes, infections, and smoking.