In placental mammals, the umbilical cord (also called the navel string, birth cord or funiculus umbilicalis) is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord is physiologically and genetically part of the fetus and (in humans) normally contains two arteries (the umbilical arteries) and one vein (the umbilical vein), buried within Wharton's jelly. The umbilical vein supplies the fetus with oxygenated, nutrient-rich blood from the placenta. Conversely, the fetal heart pumps low oxygen, nutrient-depleted blood through the umbilical arteries back to the placenta.

 

Note:   The above text is excerpted from the Wikipedia article Umbilical cord, which has been released under the GNU Free Documentation License.