To best understand the placenta we must first try to understand the nature of the baby in utero. From the instant of conception to the moment of birth the baby never once comes in direct contact with the mother, yet it is fully dependent on the mother for its survival. How is this possible? The answer is the placenta. Because most of the baby's organs like its kidneys and lungs are non-functional (in practical terms, though they do exhibit some elementary form of functionality) during the first 9 months in utero, the baby depends on the mother's equivalent organs for its own survival. If the baby wants to rid itself of waste it must do so through the mother. Likewise, if the baby wishes to breath, in other words to circulate oxygen throughout its body, it must obtain that oxygen from the mother. Most people know about the umbilical cord and how it is a "life line" between the mother and child, but what many people do not realize is that the umbilical cord is nothing more than a hallway or tunnel facilitating the two-way transportation of vital nutrients or harmful wastes to and from the fetus, all of which are filtered through the placenta. The placenta itself is much like an organic sponge but one, which grows as the baby grows, and whose porous spots are constantly filled with blood from the mother. The organic part of the placenta therefore acts much like the revolving door of an office building, facilitating the transfer of nutrients and wastes from the blood supplies of the mother and fetus. You can have all the tunnels you want leading up to a building's doors; if the doors are locked then everyone in the building will starve.