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UMBILICAL CORD
In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to its placenta. It contains one or two major veins, buried within Wharton's jelly, for the exchange of nutrient- and oxygen-rich blood between the embryo and placenta.
In the third stage of labour, the uterus expels the placenta along with the cord from the mother's body. After the cord is separated from the placenta, the umbilical stub on the newborn's belly dries and comes off after a few days. It leaves only a small scar (the umbilicus) behind.
In humans, the cord is clamped or cut after birth. The umbilical cord is made of Wharton's jelly, not ordinary skin and connective tissue. There are no nerves, so cutting it is not painful. There is ordinarily no significant loss of either infant or maternal blood while cutting the cord. In some cultures the umbilical cord is cut by the father of the baby. Lotus Birth is a practice of leaving the cord uncut after birth so that the baby is left attached to its placenta until the cord naturally separates. This is usually 1–3 days.
In case of animals, the mother bites the cord off separating the placenta from the baby. It is usually consumed by the mother which recycles the protein, and reduces tissue that would attract scavengers or predators.
The umbilical cord develops from, and contains, remnants of the yolk sac and allantois. In humans, the umbilical cord in a full term fetus is usually about 50 cm long and about 2 cm in diameter.
Cord blood
Recently, it has been discovered that the blood within the umbilical cord, known as cord blood, is a rich and readily available source of primitive, undifferentiated stem cells (i.e. CD34+ and CD38-). These cord blood cells can be used for bone marrow transplant.
Some parents have opted to have this blood harvested upon the baby's birth, and frozen for long-term storage at a cord blood bank should the child ever require the cord blood stem cells (for example, to replace bone marrow destroyed when treating leukemia). This practice is somewhat controversial.
Problems
A number of abnormalities can affect the umbilical cord, which can cause problems that affect both mother and child:
Other uses for the term "umbilical cord"
The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the hose connecting a surface-supplied diver to his surface supply of air and/or heating, 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.
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