The Function of the Belly Button (Navel)
The belly button, or umbilicus, is the scar that remains after the umbilical cord detaches following birth, marking the site where nutrients and oxygen were delivered to the developing fetus during pregnancy.
Embryological Development and Formation
- The umbilicus appears as early as the fourth week of fetal life during the folding of the embryonic plate, initially forming as a primitive umbilical ring on the ventral aspect of the body 1
- The primitive umbilical ring contains the connecting stalk, umbilical vessels, vitelline duct and vessels, allantois, and loop of intestine 1
- These structures eventually form the definitive umbilical cord, which contains three umbilical vessels (one vein and two arteries) embedded in Wharton's jelly 1
Physiological Function
During fetal development, the umbilical cord serves as the lifeline between mother and fetus, allowing for:
After birth, the umbilical vessels inside the body obliterate and gradually form ligaments 1
- The umbilical vein becomes the ligamentum teres (round ligament of the liver)
- The umbilical arteries become the medial umbilical ligaments
Clinical Significance
The umbilicus is considered a "mirror of the abdomen" in newborns and can reveal various congenital abnormalities 1
Congenital disorders at the umbilicus may include:
- Herniation (umbilical hernia)
- Bleeding
- Discharge of mucous, urine, or feces 1
Umbilical cord abnormalities can be associated with intrauterine fetal demise (IUFD), particularly:
- Cord stricture
- Abnormal coiling
- Hemorrhage
- Thrombosis
- Edema 3
In cases of multiple loops of umbilical cord around body parts, there can be increased risk of:
- Growth restriction
- Fetal demise in severe cases 4
Evolutionary Perspective
- The umbilical scar is present in all amniotes (mammals, reptiles, and birds) at least early in their ontogeny 2
- Recent paleontological evidence has identified an umbilical scar in a ~130-million-year-old dinosaur fossil (Psittacosaurus), representing the oldest known preserved umbilicus 2
- Unlike most modern reptiles and birds that lose this scar within days to weeks after hatching, some species retain a visible umbilical scar into adulthood, similar to humans 2
Surgical Considerations
- In abdominoplasty procedures, particularly for massive weight loss patients, reconstruction of the umbilicus is an important aesthetic consideration 5
- Techniques like the "inner scar umbilicus" have been developed to create natural-looking navels with minimal visible scarring 5
The belly button serves as a permanent reminder of our prenatal development and the vital connection we once had to our mothers through the umbilical cord.