Placenta (Latin)

At the beginning of the fetal period, the placenta has two components: a portio fetalis, formed by the chorion frondosum, and a portio maternalis, formed by the decidua basalis. On the fetal side, the placenta is bordered by the chorionic plate. On its maternal side, it is bordered by the basal decidua. The placenta is the meeting point of two circulatory systems: fetal circulation and maternal circulation. The maternal component of the placenta contains aa. maternae and vv. maternae that feed into the intervillous spaces. On the opposite side, the aa. umbilicales and vv. umbilicales form a tree-like structure within the spatium intervillosum. Here, the fetal and maternal blood comes into close contact separated only by a thin membrane, called the placental membrane.