10 Flexible Facts About the Tongue

The human body is an amazing thing. For each one of us, it’s the most intimate object we know. And yet most of us don’t know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

Your tongue is good for a lot more than eating an ice cream cone or a giving a rude gesture during a moment of road rage. Not only does the tongue play a crucial role in your sense of taste, it’s important to breathing, swallowing, speaking, and singing.

Your tongue is actually made of eight interwoven, striated muscles that can move in any direction. It’s thick with glands and fat, and covered in a mucus membrane, which is why it’s always moist. Here, Erich Voigt, otolaryngologist and clinical associate professor at NYU Langone Medical Center, reveals to Mental Floss some underappreciated facts about the tongue.


They're also clustered along the sides and at the back; the middle of the tongue is the least receptive area. The tongue is covered with tiny nodes called papillae, which house your taste buds, as well as the serous glands, required for the act of tasting.


That tongue map with different zones for different flavors that we all grew up learning? It's wrong. All taste buds are capable of detecting the five types of taste (sweet, sour, salty, bitter, and savory), though different receptors are more responsive to different flavors.


If you’ve ever wondered why you used to be able to enjoy a mouthful of sugar and now find candy too sweet, it’s probably because the types of taste buds you have change as you age. Kids' taste buds are more sensitive to sweet tastes than adults' tongues are. “It explains why children really enjoy sweets and candies, as compared to adults who may enjoy more complex flavors and spices,” Voigt says. There are likely evolutionary reasons for this sweet, er, tongue.


When a fetus is developing, says Voigt, the embryonic thyroid gland “starts in the tongue and then descends down the neck as a child forms.” In certain rare cases, the thyroid doesn’t drop, and can be located in the base of the tongue at birth. This is called a lingual thyroid, and requires removal and medication. This condition may not be caught right away—usually doctors don’t notice until symptoms of hyperthyroidism turn up, or a goiter, a swelling of the thyroid, appears.


It's a common misconception, says Voigt. But depending on how you measure strength, that title could be more justifiably claimed by the heart, the jaw bone's masseter, or the gluteus maximus in your butt. While the tongue is very strong because “it’s made up of many muscles both intrinsic and extrinsic,” Voigt says, its notability lies in its flexibility. The tongue has unique biomechanics—unlike other muscles, it doesn't surround any supporting bones, and it needs to be able to make three-dimensional changes in shape to handle all the speaking, eating, and swallowing we require of it.


Can’t make a fleur de lis with your tongue? Not your mom’s fault. It turns out that the longstanding belief that the ability to roll, flip, and bend your tongue is a genetic trait is not true. John McDonald, an evolutionary biologist at the University of Delaware, recently debunked this myth in an NPR interview. If such an ability were genetic, then identical twins would both be able to do it, which is not the case, as was shown in a 1952 study by geneticist Philip Matlock.


Actually, it has two, and they're distinctly different, which Voigt says is atypical. “The tongue has very unique nerve innervation. The anterior [forward] two-thirds gets a different nerve from the posterior [back] one third,” he says.


Geographic tongue is an unusual condition in which a loss of the tiny papillae that normally cover the tongue’s surface creates irregular raised, red patches on the tongue that can resemble continents or islands on a map. Doctors don’t understand the causes of this bizarre condition, though stress, allergies and eating habits may be responsible. Voigt says, in some cases, those patches “might even grow hair.”


The human papillomavirus (HPV) is a sexually transmitted disease that typically afflicts the genitals of humans. It can result in genital warts and is a risk factor for cervical cancer. Unfortunately, says Voigt, “The base of the tongue is one of the increasing forms of cancer due to infection from HPV, which is spread there through oral sex.” Other forms of tongue cancer can result from drinking alcohol, chewing tobacco, and chewing betel nut.


In Tibet, sticking out your tongue is a considered a polite greeting between two people when they meet. And among the Maori people of New Zealand, sticking out the tongue is part of a ritual called a haka, where men stick out their tongues in a simulated war dance to intimidate the enemy.

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.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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.