We have the umbilical vein, and we have the umbilical artery. And the umbilical cord also actually contains two types of extra embryonic membranes. It contains the lantos and it also contains the umbilical vesicle, also known as the yolksac. And the corian is the third type of extra embryonic membrane. Now, the next question is what exactly is the function? What is the purpose of the placenta?