Dr. Universe explains belly buttons

Ask Dr. Universe is a science-education column from Washington State University.

  • Thursday, January 17, 2019 3:00pm
  • Life
Illustrations by Rob McClurkan

Illustrations by Rob McClurkan

Dr. Universe: Why do we have a belly button? – Jane, 9, Kennewick, WA

Dear Jane,

Whether you have an innie or an outie, pretty much all us mammals have a belly button. But before you had a belly button, there was actually a different bit of anatomy in its place.

While you were still growing inside of your mother, a small, bendy tube on your tummy connected the two of you. This tube is how you got pretty much everything you needed to grow before you were born into the world.

When a mother eats something—maybe it’s salad or ice cream—she gets different nutrients like proteins, fats, and vitamins from the food. The tube, or umbilical cord, helps her pass along the different nutrients so the baby can grow.

That’s what I found out from my friend Gina Cronrath, a nursing instructor at Washington State University. She also told me the umbilical cord helps remove waste from the baby, as well.

“After the baby is born, it can drink on its own and go to the bathroom into a diaper,” she said. “So the umbilical cord isn’t needed.”

It actually isn’t until about five weeks into a mother’s pregnancy that the umbilical cord starts to grow—and it will keep growing until the cord is about two feet long. A pregnant mother’s belly can really stretch out. Sometimes a mother will even get a temporary outie belly button. Then it will return to an innie.

After a baby is born, a doctor, midwife or birth partner will help cut the umbilical cord. Don’t worry, though—it doesn’t hurt the mother or the baby. Unlike, say, your skin, the cord doesn’t have nerves that would help you sense pain. It actually has a kind of jelly-like texture and this substance helps protect the blood vessels inside of the cord.

A small part of the cord will stay attached to the baby’s belly for a couple of days before it falls off. What’s left is a brand new belly button. Or if you want to use the more scientific name, it’s a brand new navel.

It turns out that a lot more humans have innies than outies. It all depends on how the muscles and skin heal up after the cord is cut. In a way, the belly button is the body’s first scar.

From big blue whales bellies to furry cat bellies to human bellies, mammals share a connection to their mothers through the umbilical cord. After you are born, what was once a big part of your survival doesn’t serve much purpose anymore—except for maybe collecting a bit of lint.

One thing is for sure, your question really got me contemplating my navel in a whole new way. And as Cronrath put it, our belly buttons are a kind of reminder that our mothers took care of us right from the beginning.

Sincerely,

Dr. Universe

More in Life

Registering to vote online or in-mail ends Monday

In-person registration is available up until Election Day, Aug. 6.

Cruz the Loop and Return to Renton Benefit Car Show set for July 6, 7

Hot Rod weekend, downtown, will have some street closures.

Join author Kurt Armbruster for a discussion of his latest book, “Pacific Coast, Seattle’s Own Railroad” at 6 p.m. May 16 at the Renton History Museum, 235 Mill Ave. S. Courtesy photo
Upcoming events: Pacific Coast Railroad history lesson; coffee with Renton cops

Symphony: Bellevue Youth Symphony Orchestra Spring Masterworks Concert will highlight Tchaikovsky’s Symphony… Continue reading

Renton Rotary’s Youth of the Month for May

Five Renton students were selected as May 2019 Youth of the Month to finish off the school year.

Gardeners love our veggie-friendly Western Washington climate

Here are the most incredible edibles to grow now.

A look back at Black River

Renton History Museum hosts event with Seattle writer and natural history expert David Williams.

It is a busy time in the garden with planting

Near the end of April the nurseries will be overflowing with color.… Continue reading

Thom Cantrell, one of the organizers of the upcoming International Conference for Primal People, holds up a mould of a Sasquatch footprint. He said the mould was taken in the Blue Mountains in Oregon by Paul Freeman, a well-known Sasquatch hunter who’s 1994 footage of a Sasquatch in that area made big waves in the believer and skeptic communities alike. Photo by Ray Miller-Still
All things Sasquatch in Enumclaw

Washington state is famous for countless reasons. It’s the birthplace of Starbucks… Continue reading

RHS Students gear up for Bubblin Brown Sugar dance competition

The competition is April 27 at Garfield High School.

Special police partners honored

King County Sheriff’s Office dedicates new memorial to honor K9 service dogs and handlers.