Umbilical Cord

Though formed from an egg, human embryos do not depend on egg yolk for nourishment. The human egg does include an egg sac, but it degenerates early in pregnancy. Instead, the embryo forms a connection to the cells that will become the placenta through a body stalk, which later becomes the "umbilical cord." Running between the placenta and the abdomen of the fetus, the rope-like cord is a new organism's lifeline. It contains two arteries and one vein, through which the baby's heart pumps blood carrying nutrients or wastes to and from the placenta. The cord is about a half an inch in diameter and is usually some twelve to thirty-five inches in length - a little longer than the average baby.