From Fetal Development to Birth
The belly button, or navel, is a visible scar on the abdomen, representing where the umbilical cord once connected a baby to its mother. Its internal connections are rooted in our development before birth.
During pregnancy, the umbilical cord serves as a lifeline, facilitating the exchange of nutrients, oxygen, and waste between the developing fetus and the mother. It typically includes two umbilical arteries, which carry deoxygenated blood and waste products away from the fetus, and one umbilical vein, which delivers oxygen and nutrient-rich blood to the fetus.
Beyond these vessels, the umbilical cord also houses the urachus, a tube that links the fetal bladder to the allantois, a sac that collects fetal urine within the womb. Another temporary structure is the vitelline duct, which connects the primitive gut of the embryo to the yolk sac, providing early nourishment.
Upon birth, the umbilical cord is clamped and cut, severing the physical connection between mother and baby. The remaining stump of the cord typically dries and falls off within one to three weeks, leaving behind the distinct belly button. This process marks the end of these fetal structures’ active roles, initiating their transformation within the body.
Internal Structures in Adulthood
After birth, umbilical cord components transform into fibrous ligaments. The two umbilical arteries shrivel, becoming the medial umbilical ligaments. These fibrous cords extend from the internal iliac arteries towards the navel, supporting the bladder on the inner abdominal wall.
The single umbilical vein transforms into the round ligament of the liver (ligamentum teres hepatis). This fibrous band runs from the navel to the liver, anchoring it to the anterior abdominal wall.
The urachus, which connected the fetal bladder, closes off to become the median umbilical ligament. This ligament extends from the bladder to the navel, situated in the midline of the lower abdominal wall. The vitelline duct normally disappears, leaving no trace in adulthood.
In adults, the belly button is not directly connected to the intestines or any other internal organs. These fibrous structures serve as anatomical landmarks and provide some structural support within the abdominal cavity.
When Connections Cause Concerns
While the obliteration of fetal structures is a normal process, sometimes these connections do not close completely, leading to various medical conditions. One common issue is an umbilical hernia, where a portion of the intestine or other abdominal contents protrudes through a weak spot in the abdominal wall near the navel. This often appears as a bulge and may be more noticeable when crying or straining.
Anomalies related to the urachus can also occur if it fails to fully close. A patent urachus means the tube remains open, allowing urine to leak from the bladder through the navel. Other urachal anomalies include urachal cysts, which are fluid-filled sacs that form along the path of the urachus, or an urachal sinus, a blind-ended tract that opens at the navel but does not connect to the bladder. These conditions can lead to discharge, infection, or abdominal pain.
Remnants of the vitelline duct are another category of concern. The most common is Meckel’s diverticulum, a small pouch that extends from the wall of the small intestine, representing a persistent portion of the vitelline duct. While often asymptomatic, it can cause bleeding, inflammation, or obstruction, mimicking appendicitis.
In rare cases, a vitelline fistula may persist, creating an open connection between the small intestine and the navel, potentially leading to discharge of intestinal contents.