The belly button, or navel, is a permanent mark of our earliest connection to life. It is fundamentally a scar resulting from the detachment of the umbilical cord, the temporary organ that sustained us in the womb. This feature is shared among placental mammals and reminds us of the complex developmental process that occurs before birth.
The Umbilical Cord’s Prenatal Function
The umbilical cord is a biological lifeline that connects the developing fetus to the placenta throughout gestation. This structure is the sole conduit for the exchange of all necessary materials between the maternal and fetal circulatory systems. The cord itself is a complex bundle of blood vessels encased in a protective, gelatinous substance called Wharton’s jelly.
A typical human umbilical cord contains three vessels: one large umbilical vein and two smaller umbilical arteries. The single umbilical vein is responsible for transporting oxygenated, nutrient-rich blood from the placenta directly to the fetal heart. Conversely, the two umbilical arteries carry deoxygenated blood and metabolic waste products from the fetus back toward the placenta. This system ensures the fetus receives a constant supply of energy and oxygen while efficiently eliminating its waste.
The placenta acts as the fetus’s temporary lungs, kidneys, and gastrointestinal system. The umbilical cord facilitates this exchange, carrying a significant volume of blood, which can reach approximately 240 milliliters per minute near term. This blood flow is necessary for the fetus to grow and develop until birth.
The Scarring Process From Cord to Navel
The transition from a functional cord to a scar begins immediately after birth when the newborn no longer requires the placental connection. A healthcare provider clamps and cuts the cord, a procedure that is painless because the cord contains no nerves. This action leaves a small, fleshy remnant attached to the baby’s abdomen, referred to as the umbilical stump.
Over the next one to three weeks, the tissue of the remaining stump undergoes a natural process of drying and shriveling. During this time, it changes color, turning from a pale, yellowish-green to a dark brown or black. The entire stump eventually detaches on its own, similar to a scab falling off, leaving a fresh, healing wound.
The resulting navel is the scar tissue that forms where the abdominal wall closed around the retracted umbilical vessels. The speed and nature of this healing determine the final appearance of the belly button. Parents are advised not to attempt to pull the stump off, even if it is barely attached, as this can delay the healing process and potentially cause bleeding or infection.
Anatomy and Common Variations
The navel is a complex, three-dimensional scar formed by the fusion of skin and underlying connective tissue at the point of the former umbilical ring. The final shape of this scar is determined by factors like the amount of subcutaneous fat, the tautness of the abdominal fascia, and the way the skin naturally retracts during healing. Despite common belief, the manner in which the cord is cut does not influence whether a person ends up with an “innie” or an “outie” belly button.
The vast majority of people have an “innie,” or inverted navel, where the scar tissue settles inward, creating a depression. An “outie,” or protruding navel, occurs when the scar tissue or underlying structures heal in a way that pushes the skin outward. One common cause for a significant outie is a small umbilical hernia, which is a benign condition where a section of intestine or fat pushes through a slightly open spot in the abdominal muscle wall near the navel.
Umbilical hernias are common in infants and often resolve spontaneously as the abdominal muscles strengthen, typically by the age of five. Less common causes for a protruding navel include an umbilical granuloma, which is a small, moist, reddish lump of scar tissue that can form after the stump falls off. In either case, the shape is a result of individual healing variations.
Modern Purpose and Care Considerations
After the umbilical cord stump has healed and fallen off, the navel serves no necessary biological function in the adult body. It is considered a vestigial structure, though it remains a useful anatomical landmark for medical professionals and surgeons. Healthcare providers often use the navel to visually divide the abdomen for diagnostic purposes.
The primary consideration for the navel in daily life is basic hygiene, as its recessed shape can sometimes trap debris and moisture. Cleaning the navel with soap and water during a regular shower is usually sufficient to prevent the buildup of lint, sweat, and dead skin cells. Failure to maintain cleanliness can lead to irritation or minor, localized infections.
In infants, care is focused on the healing umbilical stump until it drops off naturally. Parents are instructed to keep the area clean and dry, often by folding the diaper below the stump to expose it to air. Any signs of infection, such as persistent bleeding, foul-smelling discharge, or significant redness around the navel, warrant immediate consultation with a healthcare provider.