The belly button, or navel, is a recognizable feature on the human abdomen. It serves as a scar, marking the site where the umbilical cord was once attached during fetal development. While it might seem like a simple indentation, its origin traces back to a temporary connection essential for early life.
The Umbilical Cord’s Role in Fetal Development
During gestation, the umbilical cord connects the developing fetus to the placenta within the mother’s uterus. This flexible, tube-like structure contains three primary blood vessels: two umbilical arteries and one umbilical vein, encased in a protective gelatinous substance.
The umbilical vein carries oxygenated blood and nutrients from the placenta to the fetus. Conversely, the two umbilical arteries transport deoxygenated blood and metabolic waste products from the fetus back to the placenta. This continuous exchange supports fetal development. The umbilical cord’s existence is temporary, designed to support the fetus only until birth.
Transformation After Birth
Immediately following birth, the umbilical cord’s function ceases as the newborn begins to breathe independently and its circulatory system adapts. Healthcare providers clamp and cut the cord a few centimeters from the baby’s abdomen. This procedure is painless for the newborn as the cord contains no nerves.
The remaining umbilical stump, typically 2 to 3 centimeters long, gradually dries, shrivels, and darkens over the next one to three weeks. It then naturally detaches, leaving the characteristic belly button scar. Internally, the blood vessels within the cord also undergo significant changes.
These internal vessels are no longer needed for circulation and begin to close off and atrophy. This process transforms the former blood vessels into fibrous cords or ligaments. These newly formed ligaments become permanent anatomical structures within the adult abdominal cavity, marking the path of the original umbilical vessels.
Adult Remnants and Their Connections
In an adult, the belly button itself is a scar and does not directly connect to internal organs. However, the internal remnants of the umbilical cord’s vessels persist as fibrous ligaments within the abdominal cavity, serving as anatomical landmarks. These structures are no longer functional in terms of blood flow but indicate the pathways of the fetal circulatory system.
One such remnant is the round ligament of the liver. This fibrous structure is what remains of the umbilical vein, which once carried oxygen-rich blood to the fetal liver. In adults, it is found within the falciform ligament, extending from the navel region to the liver.
Another pair of remnants are the medial umbilical ligaments, which are derived from the umbilical arteries. These two ligaments extend from the internal iliac arteries, running along the inner surface of the anterior abdominal wall towards the belly button area. They are found on either side of the bladder and are typically non-functional in adults.
Finally, the median umbilical ligament is a fibrous cord formed from the urachus, a tube that connected the fetal bladder to the umbilical cord. This ligament extends from the apex of the bladder to the umbilicus. While generally benign, persistent remnants of the urachus can occasionally lead to conditions such as urachal cysts or fistulas.