11 Facts About the Thumb

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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.

When it comes to the fingers on your hand, the thumb definitely does its own thing. Thumbs only have two bones, so they're obviously shorter, and they play a very important role that no other finger can claim; thanks to their unique saddle-like joint shape, and a little muscle known as the abductor pollicis brevis, you can bend and stretch your thumbs opposite your fingers to grip things. This is why they're known as "opposable thumbs." To bring you these 11 facts about the thumb, Mental Floss spoke with three experts on this unique digit: Barbara Bergin, an orthopedic surgeon in Houston; Loren Fishman, medical director of Manhattan Physical Medicine and Rehabilitation, in NYC; and Ryan Katz, attending hand surgeon at the Curtis Hand Center, located at the Medstar Union Memorial Hospital in Baltimore.

1. OPPOSABLE THUMBS MAY HAVE FREED UP OUR ANCESTORS' MOUTHS FOR LANGUAGE.

The evolution of a thumb helped our ancestors evolve to be better at defense, allowing for throwing and clubbing activities. Moreover, Fishman says, it may have even contributed to our cognitive function. "Some say this is why we have language," he says, "because we can hold things in our hands and [therefore] use our mouths for something else—such as discussing the functions of the thumb."

2. THUMBS HAVE THEIR OWN PULSE.

You might have noticed that medical professionals take a pulse with the middle and index finger. The reason is because there's a big artery in the thumb, the princeps pollicis artery, and arteries pulse, making it difficult to feel a pulse in a neck if you're using your thumb.

3. THE THUMB SEPARATES US FROM OTHER ANIMALS. MOSTLY.

"The thumb is wonderful. It evolved in such a way that we can use it to do so many amazing things, and it's one of the things that separates us from other animals," Bergin says. A handful of other animals, mostly primates, have opposable thumbs, or toes, as the case may be. These include orangutans, chimpanzees, a phylum of frogs known as phyllomedusa, some lemurs, and giant pandas—although their thumb-like apparatus is really just an extra sesamoid bone that acts like a thumb.

4. TOES CAN BECOME THUMBS.

If you should lose a thumb, fear not, says Katz. "It can be rebuilt by surgeons using your big toe." This specialized surgery uses microvascular surgery techniques to transfer your big toe to your hand, where it will function almost exactly as your thumb did. "The toe is then brought to life by sewing together small arteries and veins under a microscope," Katz says, a complicated surgery that has become vastly more sophisticated over the years. The second toe can be used too, as you can see in this medical journal, but we warn you: It's not for the faint of heart.

5. … BUT IS A THUMB WORTH LOSING A TOE OVER?

It may not seem like a big deal to lose one thumb—after all, you've got another one. But Katz cites the American Medical Association's "Guides to the Evaluation of Permanent Impairment" [PDF], which states your thumb is so important that a complete amputation "will result in a 40 percent impairment to the whole hand." In fact, they claim that it would take "a complete amputation of the middle, ring, and small fingers to equal the impairment of an amputated thumb."

6. IT'S BETTER THAN HAVING YOUR HAND SEWN TO YOUR FOOT.

Katz also points out that "there used to be a common surgical procedure for thumb reconstruction, where the patient's hand was sewn to their foot for a period of time." This procedure was called the Nicoladani procedure, after the German surgical innovator Carol Nicoladoni. "It was a precursor to transplant surgery and plastic or reconstructive surgery as we know it today," he says.

7. YOUR THUMB MAKES AN ASTONISHINGLY WIDE VARIETY OF MOTIONS.

Other than pinching and grasping, Katz points out that the thumb "translates, rotates, and flexes all at once." This coordinated set of motions provides strength and dexterity. "Thus it's the thumb that allows us to easily pen an essay, turn a nut, pick up a coin, or button a shirt."

8. THAT DEXTERITY ALSO MAKES IT FRAGILE.

The thumb may appear to only have two knuckles, but it actually has a third, right above the wrist. This is called the first carpometacarpal joint. If that starts to hurt, or gets big enough to look like a bump or a mass, you may have carpometacarpal joint disorder (CMC), a common condition that is partly genetic and partly from repetitive use, according to Bergin. "You can get arthritis in the other joints, too, but this one is the most debilitating," she says. "First it becomes painful, and then you lose the ability to use it." Surgery can help with the pain, but it won't restore full mobility.

9. PAIN IN YOUR THUMB MAY REQUIRE LIFESTYLE CHANGES.

Bergin suggests small lifestyle changes so you don't need to grip anything too hard can make a huge difference, such as buying milk jugs with handles or using an electric toothbrush. "There are a lot of things we can do [to help] on a daily basis that shouldn't affect our quality of life," she suggests.

10. SWIPING RIGHT MIGHT BE DANGEROUS.

While we generally associate thumb arthritis with older people, Bergin says she now sees it in people in their forties and even thirties. Other studies have suggested that frequent phone use can be damaging. "There must be a genetic component to premature wearing of the thumb," she says. If it runs in your family, it's a good idea to be proactive and try to avoid repetitive gripping activities.

11. WHAT IT MEANS IF YOUR THUMB IS NUMB.

If instead of pain you're experiencing numbness of the thumb that extends to your index and middle fingers, you may be showing early symptoms of carpal tunnel syndrome. Fortunately, this isn't an emergency. "The condition takes a long time to become a big problem" Bergin says. People can sometimes help the condition by wearing wrist braces and getting physical therapy. If you just can't take it, "you can get surgery at any point if you failed to improve with bracing," she says. The surgery can reduce mobility, but it should take away the numbness and pain.

10 Smart Facts About Your Gut

Colorized scanning electron micrograph of E. coli, a common gut bacteria
Colorized scanning electron micrograph of E. coli, a common gut bacteria
National Institute of Allergy and Infectious Diseases, Flickr // CC BY 2.0

Gut feelings get all the press, but your gut may be more of a thinker than you know. Some scientists now consider it a second brain. While it won’t necessarily help you study for an exam or get a promotion, your gut can influence the chemistry of your mood, emotions, immune system, and long-term health. Research even suggests the gut can “learn” new tricks through conditioning. These powerful connections are part an emerging field of science called neurogastroenterology designed to study the gut-brain link. Here are 10 facts you may not know about your gut.

1. THE GUT DOESN'T NEED THE BRAIN'S INPUT. 

You might think of your gut as a rebel against authority. It doesn’t wait for your brain’s impulses to do the important work of digestion, because it doesn’t need to—it acts as its own “brain.” No other organ, not even the all-powerful heart, can pull that off.

2. THERE ARE MORE THAN 100 MILLION BRAIN CELLS IN YOUR GUT.

Your gut’s power to think for itself is no surprise; there are millions of neurons in its lengthy coils (9 meters of intestines, from esophagus to anus). That’s more neurons than are found in the spinal cord or peripheral nervous system.

3. YOUR GUT HAS ITS OWN NERVOUS SYSTEM.

The enteric nervous system—the controlling mechanism of digestion and elimination—is the overlord of your gut, and functions all on its own. Some scientists see it as part of the central nervous system, while others consider it its own entity. It likely evolved to give the gut the go-ahead when the “got to go” impulse strikes, without requiring the brain’s sign-off, particularly when you consider the helplessness of an infant with its brand-new brain.

4. THERE'S AN INFORMATION HIGHWAY FROM YOUR GUT TO YOUR BRAIN.

There’s one big visceral nerve embedded in your gut—the vagus nerve. Research has revealed that up to 90 percent of its fibers carry information from the gut to the brain, rather than the other way around. In other words, the brain interprets gut signals as emotions. So you really should trust your gut.

5. MOST OF YOUR SEROTONIN IS IN YOUR GUT.

Some 95 percent of your body’s serotonin, that marvelous mood molecule that antidepressant drugs like Prozac keep in your body, can be found in the gut. So, it’s no wonder that diet, medications, and antibiotics can wreak havoc on one’s mood.

6. A HEALTHY GUT MAY PROTECT YOUR BONES.

In a study of the serotonin-gut relationship, scientists discovered an unexpected link between the gut and the bones. Inhibiting the gut’s release of serotonin counteracted the bone-density reduction of osteoporosis in mice. This research is going into studies on new osteoporosis-fighting drugs.

7. RESEARCH SHOWS LINKS BETWEEN AUTISM AND HAVING FEWER STRAINS OF GUT BACTERIA. 

In as many as nine out of 10 cases, autistic people have common gut imbalances such as leaky gut syndrome, irritable bowel syndrome, and fewer strains of “good” bacteria. Research on mice is looking at possible treatments of some of the behavioral disorders of autism by balancing microbes in the guts, though many warn that such treatments can’t produce a “cure” for autism.

8. FOOD REALLY DOES AFFECT YOUR MOOD. 

Different foods, when introduced to the gut via feeding tubes, have been shown to change a person's moods without the person’s awareness of what they were "eating." Fat, for instance, increased feelings of happiness and pleasure (no surprise there) because appeared to trigger the release of dopamine—the brain’s natural opiate. Carbohydrate consumption stimulated the release of serotonin, the “feel good” neurotransmitter.

9. YOUR GUT IS YOUR BEST FRIEND IN COLD AND FLU SEASON.

Not only does your gut hold brain cells, it also houses the bulk of your immune cells—70 percent—in the form of gut associated lymphoid tissue, or GALT, which plays a huge part in killing and expelling pathogens. GALT and your gut microbiome—the trillions of bacteria that live, like an immense microbial universe, in your gut—work hard to help you get over what ails you. That’s all the more reason to be careful with the use of antibiotics, which wipe out the good bacteria along with the bad.

10. YOUR GUT CAN BECOME ADDICTED TO OPIATES.

Inside your gut are opiate receptors, which are also found in the brain. The gut is just as susceptible to addiction as the brain and may contribute to the intense difficulty some addicts have trying to kick the habit.

What Causes Hiccups?

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iStock/damircudic

The cause of hiccups depends on whom you ask. The ancient Greek physician Galen thought hiccups were violent emotions erupting from the body, while others thought they were a sign of liver inflammation. Today, evidence points to spasms in the diaphragm, the large muscle between the chest and abdomen that aids airflow during breathing. This involuntary contraction can be brought on by a number of things that might irritate the nerves that control the movement of the muscle. A full stomach, heavy boozing, rapid shifts in temperature either inside or outside of the stomach, and certain emotions like shock or excitement are all common culprits.

No matter the cause, the result is the same: The diaphragm spasms and causes us to take a quick breath. The sudden rush of air causes the epiglottis (the flap that protects the space between the vocal cords) to shut and interrupt the breath, which makes the familiar "hic" sound.

WHAT CURES THEM?

The best cure for hiccups also depends on the person you ask. Almost all cures are based on one of two principles: One type works its magic by overwhelming the vagus nerve with another sensation. The vagus nerve is a cranial nerve that innervates the stomach and conveys sensory information about the body's organs to the brain. When distracted by overwhelming information of another sort, it basically tells the brain that something more important has come up and the hiccuping should probably be stopped (vagus nerve stimulation is also used to control seizures in epileptics and treat drug-resistant cases of clinical depression). The other method for curing hiccups is to interfere with the breathing, increasing the amount of carbon dioxide in the blood, and causing the body to focus on getting rid of the of the CO2 and not making hiccups.

Swallowing a spoonful of sugar is probably the most commonly prescribed hiccup cure and falls into the first category. A teaspoon of sugar is usually enough to stimulate the vagus nerve and make the body forget all about the hiccups. Even ardent supporters of the sugar cure disagree if the sugar should be taken dry or washed down with water, though.

If this home remedy doesn't work, and your hiccups are both severe and persistent, you may need to bring out the big guns. For chronic cases like this, doctors sometimes use a cocktail of Reglan (a gastrointestinal stimulant) and Thorazine (an anti-psychotic with sedative properties) to quiet things down. In some cases that resist these drugs, Kemstro, an anti-spasmodic, is also used. Other doctors have used vagus nerve stimulators implanted in the upper chest of patients. The pacemaker-like devices send rhythmic bursts of electricity through the vagus nerve to the brain to keep the hiccup cycle in check.

Many people prefer home remedies to battle their hiccups, which may include holding your breath, gargling ice water, or breathing into a paper bag. While the same people will swear by the treatment they've been using all these years, there's no firm scientific consensus that any of them actually work. But if it helps you, isn't that all that matters?

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

An earlier version of this article appeared in 2012.

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