The navel, or umbilicus, is the permanent mark left on the abdomen after the detachment of the umbilical cord following birth. This structure served as the circulatory connection between a developing fetus and the placenta. Navel appearance varies significantly, commonly classified as an “innie” (concave) or an “outie” (convex). This physical difference often leads to the question of whether the shape of the navel is a trait encoded in our genes.
Debunking the Genetic Myth
The shape of a person’s navel is a scar, and therefore, it is not determined by heredity in the same way eye color or height is. Unlike physical characteristics that are actively programmed by DNA sequences, the umbilicus is the result of a wound healing process. There is no specific gene responsible for dictating whether the resulting scar will be an inward depression or an outward projection. Familial traits related to general skin elasticity may influence scar quality across the body, but they do not pre-determine the navel’s final contour.
The True Determinant: Scar Tissue and Healing
The final appearance of the navel is primarily determined by the specific way the remaining umbilical stump heals and the underlying anatomical structure. After the umbilical cord is clamped and cut, the residual stump naturally dries up and detaches. The skin and connective tissue must then close over the former attachment point, and the resulting scar tissue is what forms the navel. The variation between an innie and an outie depends on how the skin and scar tissue retract. An innie forms when the surrounding skin pulls inward and adheres to the abdominal wall, while an outie occurs when scar tissue protrudes outward or the skin does not retract as deeply.
Specific Reasons for a Protruding Navel
While most outies are simply a normal variation in scar formation, a distinct protrusion is sometimes caused by specific anatomical conditions. The two most common causes are an umbilical granuloma or an umbilical hernia. These conditions represent deviations from the standard healing process of the umbilical site.
Umbilical Granuloma
An umbilical granuloma is a small, moist, reddish-pink lump of tissue that develops in the navel base after the umbilical stump has fallen off. This tissue is essentially an overgrowth of scar tissue that forms when the healing process leaves behind a small area that does not completely dry out. Granulomas are generally painless and benign, but they may cause a light yellow discharge and often require simple treatment with silver nitrate to resolve.
Umbilical Hernia
An umbilical hernia is a more common cause of a prominent outie, occurring in about 20% of infants. This condition involves a small bulge that forms when a portion of the intestine or fatty tissue pushes through a weak spot in the abdominal wall near the navel. During gestation, the umbilical cord passes through an opening in the abdominal muscles which normally closes completely after birth. When the muscles fail to close entirely, the increased pressure from crying or straining can push the internal contents outward. Most umbilical hernias are harmless and resolve without intervention by the time a child is two to five years old.