The belly button, also known as the navel or umbilicus, is the scar remaining after the umbilical cord is cut at birth. This universal feature, present in all placental mammals, exhibits surprising diversity in appearance. This diversity prompts curiosity about the reasons behind these variations.
The Umbilical Cord’s Legacy
The formation of a belly button begins with the umbilical cord, a vital connection transporting nutrients and oxygen from the mother to the developing fetus. After birth, a healthcare professional clamps and cuts the cord, leaving a small stump attached to the baby’s abdomen.
This remaining stump then undergoes a natural healing process. Over approximately one to three weeks, the stump gradually dries and detaches. The site where the stump was attached then heals, forming the scar tissue that becomes the individual’s belly button.
Core Influences on Navel Shape
The initial appearance of a belly button is primarily determined by how the scar tissue forms and the surrounding anatomy. The natural healing process of the umbilical cord stump plays a significant role in whether the navel becomes an “innie” (inverted) or an “outie” (protruding). Most people, around 90%, develop an “innie” navel, which appears as an inward depression. “Outies,” where the belly button sticks out, are less common and represent a variation in how the scar tissue heals.
Genetics and individual abdominal anatomy also influence navel shape. While the method of cutting the umbilical cord does not directly determine the final shape, genetic predispositions can affect scar tissue formation and the structure of the abdominal wall. The way skin and muscles attach around the navel area contributes to its final appearance. Furthermore, the amount and distribution of subcutaneous fat and the tone of the abdominal muscles surrounding the navel can affect its depth and shape.
How Belly Buttons Evolve
Belly buttons can change in appearance throughout a person’s life due to various factors. Significant weight fluctuations alter the skin and fat surrounding the navel. Weight gain can make the navel appear deeper and wider as abdominal fat accumulates, while weight loss might cause the skin to contract, changing its shape.
Pregnancy commonly causes noticeable changes in the navel. As the uterus expands to accommodate the growing baby, it exerts pressure on the abdominal wall, stretching or flattening the belly button. An “innie” may temporarily become an “outie” during the second or third trimester due to this internal pressure. Aging also contributes to changes in navel appearance, as natural loss of skin elasticity and shifts in body composition affect its form.
External modifications, such as piercings, can intentionally alter the navel’s shape. Surgical procedures, such as abdominoplasty (tummy tucks), can also reconstruct or reshape the belly button. Medical conditions like an umbilical hernia, where tissue protrudes through a weakness in the abdominal muscles near the navel, can cause a noticeable outward bulge or change in shape.