Placenta is the vascular structure in the uterus of most mammals providing oxygen and nutrients for and transferring wastes from the developing fetus. Placentation refers to the formation or arrangement of a placenta or placentae in a woman's uterus. The placenta grows throughout pregnancy.
Placenta is a disc which is embedded in the uterine wall. It contains villi on the embryos side of the tissue. On the mothers side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo will also generate waste substances which can be removed by transferring them into the mothers blood through the placenta.