12 Facts About Belly Buttons

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Belly buttons are many things bundled up into one tiny knot: Collectors of lint. Harborers of bacteria. Objects of desire. Symbols of creation and birth. From the gross to the sexy to the spiritual, there’s a lot to unpack about the belly button’s place in history, culture, science, and religion. Let's get started.

1. THEY'RE REALLY JUST SCARS.

That little spot in the center of your belly marks the place where your umbilical cord once connected you to your mom’s placenta. When that cord is cut, a little, shriveled piece of it gets left behind. It eventually falls off—usually within the first week of a baby’s life—and what remains is a scar. Of course, “belly button” sounds a lot cuter than “belly scar.”

2. DOCTORS CAN’T CHOOSE A BABY'S BELLY BUTTON SHAPE …

Whether your belly button caves in or sticks out has nothing to do with how your doctor cut or clamped your umbilical cord. It all comes down to the amount of space between the skin and the abdominal wall, which determines how much skin—and scar tissue—is left behind. "You can't do anything to make sure babies have an innie or outie," Dr. Dan Polk, a neonatologist at Children's Memorial Hospital in Chicago, told the Chicago Tribune. "It has to do with how much baby skin leads onto the umbilical cord from the baby's body. Less skin makes an innie; more skin makes an outie." About 90 percent of people have innies, and the rest are outies. In some cases, an outie orientation is the result of an umbilical hernia, which occurs when part of the intestine pokes through the umbilical opening in the abdominal wall. It usually seals up naturally by the time a child reaches the age of 2, but more persistent cases may require surgery.

3. … BUT A COSMETIC SURGEON CAN TURN AN OUTIE INTO AN INNIE.

For those who don't like their outie, cosmetic surgery is an option—albeit a drastic one. Umbilicoplasty is a surgery that alters the size or shape of the belly button, often by removing excess skin or tightening abdominal skin. A 1971 article in the Honolulu Star-Bulletin called belly button beautification the “newest gimmick in the cosmetic surgery game.” The article cited a Japanese physician who had performed more than 3000 navel operations in the ‘60s and early ‘70s for about $80 to $150 a pop. (Now, the surgery costs about $2000 in the U.S.)

An article in The Ottawa Citizen suggested that the surgical technique dates back to the early 1900s, when it was usually done as a corrective measure in conjunction with tummy tuck surgeries, which often displace the belly button. Even if there’s no medical need, a patient can now opt for umbilicoplasty to get the “ideal” shape. “What was favored through the Greek, Roman, and Western civilization to our time is an oval belly button that is more or less vertically oriented,” New York City cosmetic surgeon Bruce Nadler told the paper in 2002, when these surgeries were starting to become more popular. By contrast, Nadler said, horizontal belly buttons are considered more desirable in Asian cultures because they’re associated with good fortune.

4. MOST MAMMALS HAVE ONE.

Dogs, chimpanzees, lions, and armadillos have one, but their navels aren’t always easy to spot. For one, most mammalian mothers chew off the umbilical cord attached to their newborns, leaving a flat scar that’s harder to detect than a human belly button. Gorillas and chimpanzees are an interesting case for navel-gazers because they have what some scientists call an “in-betweeny”—a navel that looks like a human’s but is neither an innie nor an outie.

However, there are a few notable exceptions to the mammal belly button rule. Platypuses, which lay eggs, have no umbilical cord and therefore no belly button. As for marsupials like kangaroos and koalas, their umbilical cords generally fall off while they’re still inside mom's pouch, so a scar never forms.

5. THE FEAR OF BELLY BUTTONS IS CALLED OMPHALOPHOBIA.

Some people feel anxious, afraid, or disgusted when their belly button is touched or when someone else's bare midriff is on display. This is called omphalophobia, which stems from the Greek word omphalo for navel. This fear is believed to be linked to the navel's association with umbilical cords and wombs, or perhaps the irrational childhood fear that a belly button will come undone, letting one’s guts spill out. The phobia has gained more national exposure ever since TV personality Khloé Kardashian admitted she has a fear of belly buttons.

6. IF YOU POKE IT, YOU MIGHT SUDDENLY GET THE URGE TO PEE.

Speaking of touching your belly button (and all the grossness that comes with it), you may feel a tingly sensation when you stick your finger in it. That’s because you're stimulating fibers lining the inside of your abdomen, which then send a message to your spinal cord. As Dr. Christopher Hollingsworth of NYC Surgical Associates explained to BuzzFeed, “Because your spinal cord at that level is also relaying signals from your bladder and urethra, it feels almost the same. You interpret this as discomfort in your bladder."

7. THEY CAN LEAK URINE.

In a similar vein, a rare abnormality can cause urine to leak out of the belly button. In the early stages of pregnancy, a tube called the urachus connects a fetus’s bladder and belly button and allows urine to drain. It usually atrophies and turns into a scar on the bladder at birth or soon after, but not always. Some people may never know they still have all or part of their urachus attached because it only becomes a problem if the tube doesn’t close up. In those cases, urine can travel up through the urachus and leak out of the umbilicus (navel). Surgery is generally needed to fix this issue.

8. THEY GROW SPECIAL FLUFF-CATCHING HAIRS.

Have you ever wondered why bits of lint keep collecting in your belly button, despite your best efforts to keep clean? Blame it on a special type of hair that grows in navels. These hairs have tiny barbs that protrude and rub against your clothing, causing small fibers to scrape off. The hairs are arranged in concentric circles, which act as a funnel and suck fluff into your navel. Those who shave their stomachs or don't grow a lot of body hair to begin with likely don't have many problems with lint.

9. THEY CONTAIN THOUSANDS OF KINDS OF BACTERIA.

Beyond lint, a lot of dead skin, discarded fat molecules, and thousands of bacteria also live in your navel. One 2012 study led by the aptly named Belly Button Biodiversity project documented 2368 types of bacteria in the navels of 66 study participants. Fret not, though: They help to protect you against harmful pathogens. “We know that without these microbes our immune systems won’t function properly,” the head of the project, Dr. Rob Dunn, said in a statement. “In fact, this collection of microbes must have a certain composition—must form a certain microbial ecosystem—in order for our immune system to function properly."

10. THEY USED TO BE BANNED ON TV.

In Western culture, belly buttons have been regarded as "a feminine sexual center since ancient times," according to the Online Etymology Dictionary. As such, they were deemed too lewd to show on television, according to the Code of Practices for Television Broadcasters, established by the National Association of Broadcasters in 1951. Barbara Eden, who played the titular role in I Dream of Jeannie, said network executives at NBC held meetings over whether to let her flash her navel during the show’s run in the ‘60s. Her producer, George Schlatter, “said he had never seen so many suits sitting around a table in his life discussing someone's anatomy,” Eden told the TODAY show. Although Eden’s genie get-up never ended up revealing her belly button, other shows started to push the envelope around the same time. The belly-button ban technically remained in effect until 1983, but it wasn’t exactly enforced. Yvette Mimieux of Dr. Kildare became the first actress to bare her navel on television in 1964, and others followed suit soon after.

11. THEY ARE THE SOURCE OF A LONGSTANDING THEOLOGICAL DEBATE.

Among Christians, the debate over whether Adam and Eve had belly buttons is a little like the age-old “chicken or egg” question. One popular argument holds that Adam and Eve weren’t born naturally from a mother, and thus they wouldn’t have had umbilical cords or belly buttons. Others disagree for various reasons and insist that navels have been around since the dawn of time. Both Raphael and Michelangelo depicted Adam and Eve with navels in their artwork (including the Sistine Chapel's ceiling painting), leading one 17th-century doctor and philosopher to decry these “vulgar errors,” according to the book Umbilicus and Umbilical Cord by Mohamed Fahmy. Other artists tried to avoid the issue altogether by concealing the couple’s abdomens with foliage, forearms, or long hair.

A few centuries later, a U.S. House of Representatives subcommittee refused to distribute a booklet called Races of Man to World War II soldiers because it contained pictures of Adam and Eve with navels. Members of the committee ruled that this image “would be misleading to gullible American soldiers.”

12. THEY ARE CELEBRATED IN SOME CULTURES.

Think of Middle Eastern belly dancing and midriff-baring Indian attire. In some places around the world, the navel holds cultural and even spiritual significance. Some Hindus believe that a lotus emerged from the god Vishnu’s navel, and at the center of the flower was Brahma—the creator of the universe. Likewise, in Japan, the belly button may represent the point where life begins. In the Middle Jōmon period (2500-1500 BCE), Japanese artists emphasized the appearance of navels on their human-like figurines. Today, a belly button festival is held annually in the town of Shibukawa in central Japan. “The belly button is traditionally believed to be located in the middle of the body and the most important part,” festival organizer Kazuo Yamada told Reuters. “Our town, Shibukawa, is also called the belly button of Japan, and that is how this festival began.”

Why Can You Sometimes See Your Breath?

Chalabala/iStock via Getty Images
Chalabala/iStock via Getty Images

The human body is made up of about 60 percent water, meaning that when we breathe, we don’t just exhale carbon dioxide—we also exhale a certain amount of water vapor.

Water molecules need a lot of energy in order to remain in a gaseous form. When the warm water vapor molecules from your lungs reach colder air, they condense into “tiny droplets of liquid water and ice,” according to Wonderopolis. In fact, this process of condensation is also how clouds are formed.

But it’s actually relative humidity, not just temperature, that determines whether you can see your breath. The water vapor in your breath condenses into a liquid when it hits dew point—the temperature at which the air is saturated and can’t hold any more water in gas form. Since cold air can’t hold as much water vapor as warm air, you're much more likely to see your breath on a chilly day, but that's not always the case.

On more humid days, you may be able to see your breath even when it’s relatively warm outside. That’s because the air is already more saturated, making the dew point higher. And on especially dry days, even if it's cold outside, you may not be able to see your breath at all. Dry, unsaturated air can hold more water vapor, so you can huff and puff without seeing any evidence of it at all.

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7 Facts About Blood

Moussa81/iStock via Getty Images
Moussa81/iStock via Getty Images

Everyone knows that when you get cut, you bleed—a result of the constant movement of blood through our bodies. But do you know all of the functions the circulatory system actually performs? Here are some surprising facts about human blood—and a few cringe-worthy theories that preceded the modern scientific understanding of this vital fluid.

1. Doctors still use bloodletting and leeches to treat diseases.

Ancient peoples knew the circulatory system was important to overall health. That may be one reason for bloodletting, the practice of cutting people to “cure” everything from cancer to infections to mental illness. For the better part of two millennia, it persisted as one of the most common medical procedures.

Hippocrates believed that illness was caused by an imbalance of four “humors”—blood, phlegm, black bile, and yellow bile. For centuries, doctors believed balance could be restored by removing excess blood, often by bloodletting or leeches. It didn’t always go so well. George Washington, for example, died soon after his physician treated a sore throat with bloodletting and a series of other agonizing procedures.

By the mid-19th century, bloodletting was on its way out, but it hasn’t completely disappeared. Bloodletting is an effective treatment for some rare conditions like hemochromatosis, a hereditary condition causing your body to absorb too much iron.

Leeches have also made a comeback in medicine. We now know that leech saliva contains substances with anti-inflammatory, antibiotic, and anesthetic properties. It also contains hirudin, an enzyme that prevents clotting. It lets more oxygenated blood into the wound, reducing swelling and helping to rebuild tiny blood vessels so that it can heal faster. That’s why leeches are still sometimes used in treating certain circulatory diseases, arthritis, and skin grafting, and helps reattach fingers and toes. (Contrary to popular belief, even the blood-sucking variety of leech is not all that interested in human blood.)

2. Scientists didn't understand how blood circulation worked until the 17th century.

William Harvey, an English physician, is generally credited with discovering and demonstrating the mechanics of circulation, though his work developed out of the cumulative body of research on the subject over centuries.

The prevailing theory in Harvey’s time was that the lungs, not the heart, moved blood through the body. In part by dissecting living animals and studying their still-beating hearts, Harvey was able to describe how the heart pumped blood through the body and how blood returned to the heart. He also showed how valves in veins helped control the flow of blood through the body. Harvey was ridiculed by many of his contemporaries, but his theories were ultimately vindicated.

3. Blood types were discovered in the early 20th century.

Austrian physician Karl Landsteiner discovered different blood groups in 1901, after he noticed that blood mixed from people with different types would clot. His subsequent research classified types A, B and O. (Later research identified an additional type, AB). Blood types are differentiated by the kinds of antigens—molecules that provoke an immune system reaction—that attach to red blood cells.

People with Type A blood have only A antigens attached to their red cells but have B antigens in their plasma. In those with Type B blood, the location of the antigens is reversed. Type O blood has neither A nor B antigens on red cells, but both are present in the plasma. And finally, Type AB has both A and B antigens on red cells but neither in plasma. But wait, there’s more! When a third antigen, called the Rh factor, is present, the blood type is classified as positive. When Rh factor is absent, the blood type is negative.

Scientists still don’t understand why humans have different blood types, but knowing yours is important: Some people have life-threatening reactions if they receive a blood type during a transfusion that doesn’t “mix” with their own. Before researchers developed reliable ways to detect blood types, that tended to turn out badly for people receiving an incompatible human (or animal!) blood transfusion.

4. Blood makes up about 8 percent of our total body weight.

Adult bodies contain about 5 liters (5.3 quarts) of blood. An exception is pregnant women, whose bodies can produce about 50 percent more blood to nourish a fetus.)

Plasma, the liquid portion of blood, accounts for about 3 liters. It carries red and white blood cells and platelets, which deliver oxygen to our cells, fight disease, and repair damaged vessels. These cells are joined by electrolytes, antibodies, vitamins, proteins, and other nutrients required to maintain all the other cells in the body.

5. A healthy red blood cell lasts for roughly 120 days.

Red blood cells contain an important protein called hemoglobin that delivers oxygen to all the other cells in our bodies. It also carries carbon dioxide from those cells back to the lungs.

Red blood cells are produced in bone marrow, but not everyone produces healthy ones. People with sickle cell anemia, a hereditary condition, develop malformed red blood cells that get stuck in blood vessels. These blood cells last about 10 to 20 days, which leads to a chronic shortage of red blood cells, often causing to pain, infection, and organ damage.

6. Blood might play a role in treating Alzheimer's disease.

In 2014, research led by Stanford University scientists found that injecting the plasma of young mice into older mice improved memory and learning. Their findings follow years of experiments in which scientists surgically joined the circulatory systems of old and young mice to test whether young blood could reverse signs of aging. Those results showed rejuvenating effects of a particular blood protein on the organs of older mice.

The Stanford team’s findings that young blood had positive effects on mouse memory and learning sparked intense interest in whether it could eventually lead to new treatments for Alzheimer’s disease and other age-related conditions.

7. The sight of blood can make people faint.

For 3 to 4 percent of people, squeamishness associated with blood, injury, or invasive medical procedures like injections rises to the level of a true phobia called blood injury injection phobia (BII). And most sufferers share a common reaction: fainting.

Most phobias cause an increase in heart rate and blood pressure, and often muscle tension, shakes, and sweating: part of the body’s sympathetic nervous system’s “fight or flight” response. But sufferers of BII experience an added symptom. After initially increasing, their blood pressure and heart rate will abruptly drop.

This reaction is caused by the vagus nerve, which works to keep a steady heart rate, among other things. But the vagus nerve sometimes overdoes it, pushing blood pressure and heart rate too low. (You may have experienced this phenomenon if you’ve ever felt faint while hungry, dehydrated, startled, or standing up too fast.) For people with BII, the vasovagal response can happen at the mere sight or suggestion of blood, needles, or bodily injury, making even a routine medical or dental checkup cause for dread and embarrassment.

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