Everyone has one, but you might not know much about it. Here biologist Sarah Leupen, who teaches human and comparative animal physiology, explains the ins and outs of belly buttons.
1. Why do I even have a belly button?
Your belly button, or navel – clinically, your umbilicus – is the permanent scar left from where your umbilical cord connected your circulatory system, when you were a fetus, to the placenta. Fetuses don’t breathe, eat or eliminate waste, so the placenta provides an exchange site for the mother to deliver oxygen and nutrients from her bloodstream to the fetus, as well as collecting its wastes to eliminate from her body.
Once the umbilical cord is cut, the stump dries up and falls off, revealing the baby’s navel.
Wacharaphong/iStock via Getty Images Plus
After the baby is born, the physician or other attendant cuts the cord and clamps off the stub, which then dries and falls off after about a week, leaving the point of connection – your belly button – remaining.
If the cord is not cut, as has been the practice in some times and places and as is becoming trendy again in others, it will close off after an hour or so, then naturally detach a few days after birth. Some health care practitioners are concerned that this “lotus birth” could be an infection risk, since the umbilical cord remains attached to the placenta, which is dead tissue once out of the mother’s body.
2. If it’s a scar, why doesn’t it disappear over time?
If you injure just the outer layers of your skin, as in a cut or burn, the scar will soon completely disappear, especially in young people. And newborns are very young people. But unlike in those situations, the umbilicus involves more tissue layers — not just the skin but the connective tissue underneath – so it makes sense it doesn’t just blend in with the rest of your abdominal wall once it’s healed.
What about some pretty complicated surgeries that don’t leave scars? Doctors perform many operations in ways that deliberately avoid scarring, which is not nature’s way. In fact, one way to minimize scarring for surgeries uses this existing scar – surgeons can take advantage of the navel as an incision site for removing your appendix or gall bladder or for weight-loss surgery.
But if you don’t like the way your umbilical scar looks, plastic surgery to change its appearance, called umbilicoplasty, is possible. People sometimes take this cosmetic option after pregnancy or the removal of a piercing, or just to make an “outie” into an “innie.”
Outies are much less common than innies.
Zeev Barkan/Flickr, CC BY
3. But why do some people have outies, anyway?
The look of your belly button is not related to the location of the clamp or where your doctor cut the cord.
Outies are simply an example of normal human variation, like the way some people have curly hair or dimples. When the tip…