Have you ever wondered exactly how nutrition and oxygen get from your body to the baby's? The process depends on an amazing organ, the placenta, and the baby's lifeline, the umbilical cord.

The placenta is a large soft disk that fits tightly against the inside of the mother's uterus. The mother's blood squirts onto the surface of the placenta. Fetal blood circulates through the placenta, in a rich network of capillaries along the surface. As the mother's blood flows onto these capillaries, oxygen and nutrients pass into the baby's circulation, and waste products pass back to the mom.

The placenta is attached to the baby by the umbilical cord. The belly button, or umbilicus, is the site where the umbilical cord enters the body. During fetal life, blood vessels run from there up through the liver and into the heart, which pumps the fetus's blood around its body. The most oxygen-rich blood is conveniently angled up towards the baby's brain, and after that runs through the rest of the body and back out the cord.  

When I was about nine, I remember thinking that the mother's belly button had something to do with pregnancy. Given that it pops out as the pregnancy progresses, you can see how I might have thought that. I remember being shocked when my mother pointed out that the mother's belly button developed when she was a baby and had nothing to do with the baby inside of her.