11 Facts About Fingernails

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Whether there's dirt beneath them or polish atop them, your fingernails serve more than just decorative purposes: They help keep your fingertips safe and have a multitude of special functions that even your doctor might not be aware of. “The nails occupy a unique space within dermatology and medicine in general, particularly because they are such a niche area about which few people have expertise,” Evan Rieder, assistant professor in the Ronald O. Perelman Department of Dermatology at NYU Langone Health, tells Mental Floss.

1. FINGERNAILS HAVE FOUR MAIN PARTS.

Along with skin and hair, nails are part of the body's integumentary system, whose main function is to protect your body from damage and infection. Fingernails have four basic structures: the matrix, the nail plate, the nail bed, and the skin around the nail (including the cuticle).

Fingernail cells grow continuously from a little pocket at the root of the nail bed called the matrix. The pale, crescent-shaped lunula—derived from Latin for "little moon"—on the nail itself is the visible portion of the matrix. If the lunula is injured, the  nail won't grow normally (a scarred lunula can result in a split nail), and changes in the lunula's appearance can also be signs of a systemic disease.

Fingernail cells are made of a protein called keratin (same as your hair). As the keratin cells push out of the matrix, they become hard, flat and compact, eventually forming the hard surface of the nail known as the nail plate. Beneath that is the nail bed, which almost never sees the light of day except when there's an injury or disease.

Surrounding the matrix is the cuticle, the semi-circle of skin that has a tendency to peel away from the nail. The skin just underneath the distal end of the fingernail is called the hyponychium, and if you've ever trimmed your nails too short, you know this skin can be slightly more sensitive than the rest of the fingertip.

2. THEY GROW AT A RATE OF 0.1 MILLIMETERS A DAY ...

That's about 3 to 4 millimeters per month. But they don't always grow at the same speed: Fingernails grow more quickly during the day and in summer (this may be related to exposure to sunlight, which produces more nail-nourishing vitamin D). Nails on your bigger fingers also grow faster, and men's grow faster than women's. The pinky fingernail grows the slowest of all the fingernails. According to the American Academy of Dermatology, if you lose a fingernail due to injury, it can take up to six months to grow back (while a toenail could take as much as a year and a half).

3. ... BUT NOT AFTER YOU'RE DEAD.

You've probably heard that your fingernails keep growing after death. The truth is, they don't, according to the medical journal BMJ. What's actually happening is that the skin around the base of the fingernails retracts because the body is no longer pumping fluids into the tissues, and that creates a kind of optical illusion that makes the nails appear longer.

4. ITS ESTIMATED THAT 20 TO 30 PERCENT OF PEOPLE BITE THEIR NAILS.

Scientists say it's still unclear why, but they suspect nail-biters do it because they're bored, frustrated, concentrating, or because it just feels comforting (and anxiety doesn't seem to play a big role). Perfectionists who don't like to be idle are very likely to have the habit. Biters expose themselves to the dangerous crud that collects underneath the nail: The hyponychium attracts bacteria, including E. coli, and ingesting that through nail-biting can lead to gastrointestinal problems down the line. Biting can also damage teeth and jaws.

5. HUMAN FINGERNAILS ARE BASICALLY FLAT CLAWS.

Our primate ancestors had claws—which, like nails, are made of keratin. As human ancestors began using tools some 2.5 million years ago (or even earlier), evolutionary researchers believe that curved claws became a nuisance. To clutch and strike stone tools, our fingertips may have broadened, causing the claws to evolve into fingernails.

6. THE NAIL ACTUALLY MAKES YOUR FINGERTIP MORE SENSITIVE.

While the fingernail may be tough enough to protect tender flesh, it also has the paradoxical effect of increasing the sensitivity of the finger. It acts as a counterforce when the fingertip touches an object. "The finger is a particularly sensitive area because of very high density of nerve fibers," Rieder says.

7. FINGERNAILS CAN REVEAL LUNG, HEART, AND LIVER DISEASES.

"One of the most interesting facts about fingernails is that they are often a marker for disease within the body," Rieder says. Nail clubbing—an overcurvature of the nail plate and thickening of the skin around the nails—is a particularly significant sign of underlying illness, such as lung or heart disease, liver disease, or inflammatory bowel disease. Two-toned nails—whitish from the cuticle to the nail's midpoint and pink, brown, or reddish in the distal half—can be a sign of kidney and liver disease. Nails that are two-thirds whitish to one-third normal can also be a sign of liver disease. However, little white marks on your nails, known as milk spots (or punctate leukonychia) are just the remnants of any kind of trauma to the nail, from slamming it in a door to chewing on it too fervently.

8. YOU CAN GET A COMMON SKIN DISEASE ON YOUR NAILS.

Psoriasis is "typically thought of as a skin disease, but is actually a skin, joint, and nail disease, and when severe, a marker of cardiovascular risk," Rieder says. Psoriatic fingernails may have orange patches called oil spots, red lines known as splinter hemorrhages, lifting of the edges of the nails, and pits, "which look like a thumb tack was repeatedly and haphazardly pushed into the nails," he says.

Doctors often prescribe topical or injected corticosteroids to treat psoriatic nails, but using lasers is an emerging and potentially more cost-effective technique. Rieder relies on a pulsed dye laser, which uses an organic dye mixed with a solvent as the medium to treat nail psoriasis, "which can be both medically and aesthetically bothersome," he says. This laser is able to penetrate through the hard nail plate with minimal discomfort and "to treat targets of interest, in the case of psoriasis, blood vessels, and hyperactive skin," Rieder says.

9. ANCIENT CULTURES DISPLAYED SOCIAL STATUS WITH NAIL ART.

Painting and other forms of decorating nails have a history of offering social and aesthetic cues through variations in nail color, shape, and length, Rieder says. In fact, he adds, in some cultures ornate and well-decorated fingernails "serve as a proxy for social status."

Five thousand years ago in China, men and women of the Ming Dynasty aristocracy grew their nails long and covered them with golden nail guards or bright home-made polishes. The long nails allegedly announced to the world their social rank and their freedom from performing menial labor.

10. A FORMER BEAUTICIAN HELD THE WORLD RECORD FOR THE LONGEST NAILS.

Lee Redmond of Utah started growing her nails in 1979 and kept at it until she held the world record for "longest fingernails on a pair of hands ever (female)" in 2008. Her right thumbnail was 2 feet, 11 inches and the collective length of all her nails was 28 feet, 4 inches. She also applied nail hardener daily and painted them a reflective gold. Unfortunately, she broke her nails in a 2009 car accident and has no plans to regrow them.

More recently, the man who holds the Guinness record for the "longest fingernails on a single hand—ever" chose to chop them off at Ripley's Believe It Or Not! in New York City in July 2018. Shridhar Chillal of Pune, India started growing the nails of his left hand in 1952, when he was 14 years old. At last count, the total length measured 29 feet, 10.1 inches.

11. THE FIRST NAIL CLIPPERS WERE PATENTED IN 1875.

Today, biters don't have to use their teeth to trim their nails. While the earliest tools for cutting nails were most likely sharp rocks, sand, and knives, the purpose-built nail clipper—though it might be more accurately called a circular nail file—was designed by a Boston, Massachusetts inventor named Valentine Fogerty and patented in 1875. The nail clippers we know today were the design of inventors Eugene Heim and Oelestin Matz, who were granted their patent for a clamp-style fingernail clipper in 1881.

26 Amazing Facts About the Human Body

Mental Floss via YouTube
Mental Floss via YouTube

At some point in your life, you've probably wondered: What is belly button lint, anyway? The answer, according to Mental Floss editor-in-chief Erin McCarthy, is that it's "fibers that rub off of clothing over time." And hairy people are more prone to getting it for a very specific (and kind of gross-sounding) reason. A group of scientists who formed the Belly Button Biodiversity Project in 2011 have also discovered that there's a whole lot of bacteria going on in there.

In this week's all-new edition of The List Show, Erin is sharing 26 amazing facts about the human body, from your philtrum (the dent under your nose) to your feet. You can watch the full episode below.

For more episodes like this one, be sure to subscribe here.

8 Surprising Facts About Your Nose

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iStock/AntonioGuillem

Your nose is more than just a bump on your face—it’s an important part of the respiratory system and affects many other senses, including your taste and hearing. For being something that’s so central to our daily interactions with the world, there’s still a surprising amount to discover about the nose. Here's a bit of what we do know.

1. Your nose can detect billions of different odors.

Although the human nose is weak compared to canine sniffers, our noses can detect 1 trillion smells. Strangely, scientists still aren’t sure exactly how we smell. For decades, researchers thought the olfactory system worked through receptor binding, meaning molecules of different shapes and sizes bonded to specific parts of the nose like puzzle pieces, triggering smell recognition in the brain. But recently, biophysicist Luca Turin has proposed the nose detects smell through quantum vibrations. Turin suggests the frequency at which different molecules vibrate helps the nose identify them as different scents. The theory could explain why molecules of the same shape smell quite differently. Intriguing as it is, this new theory hasn’t been tested enough to be universally accepted.

2. Our big brains might have caused our noses to protrude.

As anyone who’s been to a zoo probably knows, great apes (the closest human ancestors) have flat nasal openings—and researchers found that type of nose is far more effective at inhaling air than the human version. So what’s up with ours? Scientists think the shape might be a by-product of our big brain. The growing cerebellum forced human faces to become smaller, which probably affected the nose as well.

3. Women's noses are more sensitive than men's.

In the battle of the sexes, women’s noses come out on top. When tested for odor detection and identification, women score consistently higher than men. This might have something to do with the size of their olfactory bulb, a structure in the brain that helps humans identify smells. One study found that women have, on average, 43 percent more cells in their olfactory bulb than men do—meaning they can smell more smells.

4. Holding your nose really does help you swallow something distasteful.

Think you like chocolate just because it tastes good? Think again. Smell is responsible for 75 to 95 percent of flavor, which explains why plugging your nose helps you swallow something unappetizing. More recently, chefs and neurologists have teamed up to create meals for cancer patients and others with a diminished sense of smell, such as the elderly. Cooking meals tailored to the smell-less could help stave off depression and improve the appetite without relying on sugar and salt.

5. Surgeons can regrow damaged noses.

When people have cancer or are in an accident, the nose can become infected or even be completely destroyed. But fear not. Plastic surgeons have a way to regrow your nose—on your forehead. Using cartilage from the ribs and tissue expanders that allow the skin to stretch and grow, a new nose can be formed to replace the old one. And while a nose growing out of your forehead looks odd, it's actually one of the best places for a new nose to grow. The forehead's blood vessels can be harnessed to help grow the tissue, and removing the new nose only leaves a small scar [PDF]. Doctors have performed the procedure in the U.S., China, and India.

6. Your nose can sense more than smells.

The nose doesn’t just translate odors in the nasal passage—the tip is also full of nerves that detect pain and temperature. This helps us “smell” non-odor smells. Even people who can no longer smell things with their olfactory system can detect substances like menthol, the minty compound that makes your skin tingle. (Unfortunately, they can’t detect pure scents like vanilla.)

7. About 20,000 liters of air pass through the nose every day.

The average adult breathes around 20,000 liters of air every day, which keeps the nose quite busy. As the first line of defense for the lungs, the nose filters out small particles like pollen and dust. It also adds moisture to the air and warms it so the lungs are saved from any irritation.

8. Anosmia is just one of several smell disorders affecting the nose.

There are plenty of things that can go wrong in your nose. Allergic rhinitis, sinus infections, and broken noses are just a few. But perhaps less well known are disorders that affect the nose’s ability to smell. Anosmia is the complete inability to detect odors and can be caused by illness, aging, radiation, chemical exposure, or even genetics. Equally bizarre are parosmia and phantosmia: The former changes your perception of smells, and the latter creates the perception of smells that don’t exist. Luckily, only 1 or 2 percent of North Americans suffer from any smell disorders.

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