What is the Umbilical Cord? - Definition & Function

Lesson Transcript
Instructor: Robin Harley

Robin has a PhD in health psychology. She has taught undergraduate and graduate psychology, health science, and health education.

A fetus receives nourishment from its mother through the umbilical cord. In this lesson, the reader will learn more details about what the umbilical cord is and how it functions, including potential problems and cord blood storage. Updated: 10/12/2021

Definition of Umbilical Cord

Have you ever contemplated your navel? This part of your body, also known as the belly button, was once the entry point for a very important anatomical structure called the umbilical cord. In simple terms, the umbilical cord is a growing fetus's lifeline. It is a flexible, tube-like structure that connects a fetus to the mother's placenta. The placenta is an organ attached to the uterine wall that, in turn, connects to the mother's blood supply.

The umbilical cord carries oxygenated blood and nutrients from the placenta to the fetus through the abdomen, where the navel forms. It also carries deoxygenated blood and waste products from the fetus to the placenta. When the baby is born, the umbilical cord is cut close to the baby's body, and the stump falls off on its own. Let's look deeper at the structure and function of the umbilical cord.

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  • 0:01 Definition of Umbilical Cord
  • 0:58 Structure & Function
  • 2:14 Potential Problems
  • 3:42 Cord Blood Storage
  • 5:01 Lesson Summary
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Structure & Function

The umbilical cord forms around the fifth week of pregnancy and can grow up to 20 inches long at full-term. It is a tough, sinewy structure with two main layers: an outer layer of smooth muscle, and an inner layer containing a gelatinous fluid called Wharton's jelly. There are typically three vessels within this substance: one vein and two arteries. The vein carries oxygen and nutrient-rich blood from the placenta to the fetus, and the arteries carry deoxygenated and nutrient-depleted blood away from the fetus.

The umbilical cord enters the fetus through the abdomen and turns into two branches: one joins with the hepatic portal vein in the liver, and the other connects to the heart through the inferior vena cava. These two branches form a circuit in the fetus's body and reconnect to the umbilical cord outside. In rare cases, the umbilical cord may not develop correctly, or some other problem occurs during birth. Sometimes these problems can be detected via ultrasound before birth, but in many cases, they are not noticed until after the baby is born. Let's look at some of these potential issues and how they can affect the baby.

Potential Problems

  • Single umbilical artery: In rare cases, the umbilical cord may form with a missing artery. The cause of this is unknown, but it can lead to birth defects, including problems with the heart, nervous system, chromosomes and urinary tract. This problem can be detected before birth.
  • Umbilical cord prolapse: As the baby passes through the birth canal, the umbilical cord may prolapse, or slip into the birth canal, and become compressed by the baby during delivery. This can cut off the baby's blood supply and become a life-threatening condition if the baby is not delivered immediately.
  • Umbilical cord knots: It is not uncommon for the cord to become wrapped around the baby's neck, but this rarely causes serious problems. In rare cases, however, it may become tied in knots, and this can cut off the baby's blood supply.
  • Umbilical cord cysts: Sometimes cysts can be seen developing on the umbilical cord via ultrasound. This can lead to abnormalities in the kidneys, chromosomes and abdomen.
  • Vasa previa: In rare cases, umbilical cord blood vessels may shift outside of the protection of the cord and move underneath the baby. This can lead to tears in the vessels and life-threatening bleeding. Pregnant women who experience bleeding in the second or third trimester should seek medical attention to rule out this complication.

Cord Blood Storage

The blood inside the umbilical cord is called cord blood, and it contains undifferentiated (blood-forming) stem cells. This blood can be removed from the cord and stored in private or public banks with the intention of treating illnesses like leukemia and sickle cell anemia. Some parents decide to store this blood in a private bank in case the child or a family member needs the stem cells later in life. Private banking is the subject of some controversy. Many medical professionals discourage storage for self-use because most health conditions will already be present in the cord blood, and it is highly unlikely that the child will actually use the cells. Additionally, it is a very costly practice compared to public banking.

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