Umbilical cordIn placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to its placenta. It contains major arteries and veins for the exchange of nutrient- and oxygen-rich blood between the embryo and placenta. While the umbilical cord is functioning, the circulatory system in the fetus is very different than after birth. When the baby animal is born, the umbilical cord is severed and leaves only a small scar (the umbilicus) behind.
Recently, it has been discovered that the matrix within the umbilical cord (known as Wharton's jelly) is a rich and readily available source of primitive stem cells. Some parents have opted to have these stem cells harvested upon the baby's birth, and frozen for long-term storage should the child ever require them (for example to replace bone marrow destroyed when treating leukemia).
The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the air hose connecting a deep-sea diver to his ship or a space-suited astronaut to his spacecraft.
The phrase "cutting the umbilical cord" is used symbolically to describe a child's breaking away from the parental home.