Make note that in this term fetus, the chorion frondosum and the decidua basalis provide the fetal and maternal components of the placenta respectively. The chorion frondosum produces millions of villi that carry fetal capillaries so that the blood within them can come into close contact with maternal blood flowing through the intervillous spaces. Maternal and fetal blood do not mix in the placenta. The maternal blood flow into the placenta is through the decidua to bathe the chorionic villi and permit exchange of gasses, nutrients and metabolites between the maternal and fetal circulations. At birth, the placenta detaches from the wall of the uterus and follows the fetus. It is frequently referred to as the "afterbirth”.
Here are two views of a term placenta following its delivery after the birth of the infant. Note that the fetal side of the placenta is smooth due to the attached amnion and that the umbilical cord is attached to its center. Large profiles of the umbilical vessels can be seen radiating out from the attachemnt of the cord. The maternal side of the placenta has a bumpy "cobblestone" appearance due to the presence of cotyledons. These are produced by septa that grow into the placenta from the decidua basalis.