1.
the flexible, often spirally twisted tube that connects the abdomen of a fetus to the mother's placenta in the womb, and through which nutrients are delivered and waste expelled
2.
a cable, tube, or pipe attaching somebody or something to an essential supply, e.g. the tube that connects a deep-sea diver to an oxygen supply on a ship
3.
a long tube that connects a baby to its mother before it is born and through which it receives food and oxygenIt is cut immediately after birth.