10 Things You Might Not Know About the Elbow

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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.

Unless you bang your funny bone or regularly play tennis, it's unlikely you spend a lot of time thinking about your elbow. But without this crucial joint, many daily activities would be impossible, explains Anand Murthi, attending orthopedic surgeon and chief of shoulder and elbow surgery at MedStar Union Memorial Hospital, in Baltimore, Maryland.

1. THE ELBOW IS MORE COMPLEX THAN IT MAY SEEM.

The elbow may seem small, but it requires three bones to make its simple hinging action possible. The humerus is a long bone that runs from the shoulder socket to the radius and ulna. (And yes, there's a school of thought that believes your "funny bone"—actually your ulnar nerve—is named as a play on the word humorous.) The radius is one of the two forearm bones, running down from the elbow to the thumb side of the wrist. Lastly, the ulna stretches away from the pinkie side of the wrist. Thanks to those three bones, your arm can hinge—making it possible to do a bicep curl, lift a bag, or rotate your hand.

2. IT'S ALL HELD TOGETHER BY A KEY LIGAMENT, AS INJURED ATHLETES KNOW WELL …

The bones of the elbow are connected by numerous tendons and ligaments, including the ulnar collateral ligament, a fibrous tissue that connects the humerus to the forearm bones. This tendon is both important and vulnerable. When it ruptures or tears, you feel severe pain and can sometimes even see bruising on the inside of your arm. It's a surprisingly common sports injury, plaguing players of baseball, football, ice hockey, and golf. The other major ligament in the joint is called the radial collateral ligament. Located on the outside of the elbow, it prevents excessive extension of the elbow, and is less prone to injury.

3. … BUT THAT'S NOT THE ONLY VULNERABLE PART OF YOUR ELBOW.

At the lower end of the humerus are two rounded protrusions called epicondyles, which flare out from the bone. This is where muscles attach. The upper end of the ulna also has two protrusions, called the olecranon—which forms the pointy part of the elbow—and the caronoid process, a projection from the front of the ulna. Bone fractures, especially in children, often occur at these epicondyles, and are the most common short-term injuries of the elbow. Certain kinds of arthritis, especially in older patients with osteoarthritis, can also cause such severe degeneration here that an elbow replacement is necessary. (Since bones become more brittle as we age, it's wise to take steps to prevent falling or stumbling, as elbows are among the most likely casualties.)

4. TRAMPOLINES ARE COMMON ELBOW-BREAKERS.

Children love the thrill of a jump on the trampoline, but Barbara Bergin, an orthopedic surgeon in Austin, Texas, tells Mental Floss that she sees numerous fractures around the elbow in kids from doing just that. It's so common to break elbows and wrists this way, the American Board of Pediatrics warns against trampolines.

5. TWENTY-THREE MUSCLES GIVE YOUR ELBOW STABILITY AND FLEXIBILITY.

But the major muscles involved in bending your arm are the triceps—on the back of your arm—and biceps, on the front of your arm. Your many smaller flexor and extensor muscles allow you to move your wrists and fingers and rotate your forearm.

6. YOU DON'T HAVE TO PLAY TENNIS TO GET TENNIS ELBOW.

One of the most common conditions of the elbow is called "tennis elbow"—or lateral epicondylitis. Tennis players are prone to it, but it can be caused by any repetitive bending and flexing of the elbow, says Bergin. It's a painful degeneration of the tendons that attach to the bone on the outside of the elbow. It's so common, she says, "I probably see tennis elbow every day in my office." If the condition should strike you, Bergin says, "It's critical to stop doing whatever hurts. It will not get better if you continue to participate in whatever activity is causing pain." Full and total healing is required before you can return to the activities that gave you the condition in the first place.

7. IF IT GETS BAD ENOUGH, YOU MAY NEED "TOMMY JOHN" SURGERY.

When major league pitcher Tommy John injured his ulnar collateral ligament in 1974, his doctor opted to try a unique surgery to replace the deteriorated ligament with a tendon from somewhere else. Though the surgery can require a full year's recovery time—in Tommy John's case, it was nearly two and a half years and two surgeries—it's since become a time-tested method to repair this damaged ligament. Murthi tells Mental Floss, "New research on repairing the medial collateral ligament (versus reconstructing it) may lead to earlier recovery for Tommy John surgery. Also new treatments for articular cartilage damage, ligament reconstruction, and joint sparing techniques are evolving."

8. BUT IT'S HARD TO OPERATE ON YOUR ELBOW.

The elbow's close proximity to important blood vessels and nerves in your hand and arm make it a challenge to perform surgery on, Murthi says: "Careful, precise surgery is required to provide a good outcome. Often, rehabilitation with a skilled therapist is crucial to a good recovery." Currently, many operations are performed arthroscopically, so that surgeons can see all the various components as they make delicate maneuvers.

9. IF YOU HAVE TO GET AN AMPUTATION, HOPE FOR ONE BELOW THE ELBOW.

Should you have the misfortune of losing part of an arm, it's better to lose the parts below the elbow, Bergin says. This helps you maintain a range of motion and allows you to better manipulate a prosthesis. Fortunately, upper extremity amputations are rare and almost always result from accidents, as compared to lower arm amputations, which are often caused by some form of vascular disease.

10. EVEN JUST READING A BOOK CAN CAUSE AN ELBOW CONDITION.

While you may be tempted to read that latest hefty bestseller late into the night, if you're keeping your elbows bent in a sitting position for too long, you can get a case of ulnar neuritis, inflammation of the ulnar nerve—which can lead to numbness or weakness of the fingers and hand. Bergin warns, "It's much more common now than it used to be because we sit around for hours at a time on our phones." If you experience a "little tingly feeling in the pinky and fourth finger," she says, you've probably got a case. Her recommendation is to take as many breaks with your arms straight out as you can. Switch to a kindle or laptop that you can prop up to read at night. Be conscious of your ergonomics when you drive, type, and use your electronics.

14 Facts About Feet

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iStock/pepifoto

The foot is one of the most overworked, under-appreciated parts of the human body. Think about it: In a single day, the average person takes 8000 to 10,000 steps. That works out to be four trips around the world over a lifetime, putting a lot of wear and tear on your intricate foot bones. The foot may be humble, but its design is essential to how we walk upright, and hoofing it on two feet is a defining feature of humanity. Here are some fun—and a few funky—facts about the human foot.

1. FOOT BONES MAKE UP ABOUT A QUARTER OF ALL THE BONES IN OUR BODIES.

There are 26 foot bones in each of your feet—one less than in each hand. When we’re born, those foot bones are mostly cartilage. They only completely harden around age 21.

2. HUMANS HAVE WORN SHOES FOR A VERY LONG TIME.

When did humans begin wearing shoes, anyway? About 40,000 years ago, according to research from Washington University in St. Louis that analyzed foot bones from Neanderthals and early humans. Older specimens had thicker, stronger toes, likely from gripping the ground as they walked barefoot. That’s around the same time that the archaeological record shows a burst of artistic and technological advancements among early humans, including the first stone tools, which may have aided in the production of shoes. The oldest preserved shoe, incidentally, is 5500 years old and was found in an Armenian cave, buried in sheep dung.

3. THE BIG TOE USED TO BE A KIND OF FOOT THUMB.

This grasping toe helped our predecessors climb trees and, when young, grip onto their mothers. Thanks to modern science, if you lose your thumb, you can now replace it with a toe: toe-to-thumb transplants are a surprisingly common procedure these days.

4. FOOT BONES HOLD BIG CLUES ABOUT THE EVOLUTION OF BIPEDALISM.

Scientists are studying Homo naledi, a specimen discovered in a South African cave in 2013 that many researchers believe is a new human relative. H. naledi had very human-like feet, but with somewhat curved toe bones that suggest it climbed trees. It could be that H. naledi was beginning to experiment with walking. 

5. THERE WAS A FOOT CHEESE EXHIBITION IN IRELAND.

Warm, sweaty feet make a perfect home for bacteria, which feed on our dead skin cells and produce gases and acids that emit those arresting foot odors. They're apparently also good at cultivating cheese. An exhibition in Dublin in 2013 displayed a variety of cheeses made with bacteria samples obtained from real people’s feet, armpits, and belly buttons. Delicious. (No one actually ate any of the cheeses.)

6. FEET ARE ONE OF THE MOST TICKLISH PARTS OF THE BODY.

There’s a good reason for that: Humans have nearly 8000 nerves in our feet and a large number of nerve endings near the skin. Having ticklish feet can be a good sign: Reduced sensitivity can be an indicator of peripheral neuropathy (numbness in the feet caused by nerve damage). 

7. FOOT NUMBNESS CAN CAUSE BIG PROBLEMS FOR DIABETICS.

Complications of diabetes include poor circulation and foot numbness that can lead to serious skin ulcers, which sometimes require amputation of toes or feet. In 2010 alone, 73,000 lower-limb amputations were performed on diabetics.

8. FOOT SIZES AND WIDTHS IN THE U.S. AND UK ARE INCREASING.

Feet are spreading to support extra weight as our populations pack on the pounds. According to a 2014 study by the College of Podiatry in the UK, the average foot has increased two sizes since the 1970s. As people have grown taller and heavier, feet respond by growing. It appears many people are still in denial about their expanding feet: Though retailers are starting to respond by making larger and roomier shoes, half of women and a third of men reported they buy poorly fitting shoes. Podiatrists say ill-fitting shoes are to blame for a significant portion of foot problems, especially among women.

9. MANY GLAMOROUS CELEBRITIES HAVE BIG FEET.

From the bound feet of female Chinese elites to Cinderella and Barbie, freakishly small feet are often celebrated as more feminine. But plenty of glamorous women both past and present have had larger than average feet, among them Jacqueline Kennedy, Oprah Winfrey, Uma Thurman, and Audrey Hepburn (size 10, 11, 11, and 10.5, respectively).

10. WOMEN HAVE FOUR TIMES AS MANY FOOT PROBLEMS AS MEN.

That painful fact is often attributed to wearing heels. Ironically, Western women started wearing heels to effect a more masculine look: European men adopted the look from Persian warriors in the 17th century, and women soon followed suit.

11. THE AVERAGE PERSON WALKS ABOUT 100,000 MILES IN A LIFETIME. 

That’s a lot of stress on our feet. It’s not surprising, then, that lower back pain, headaches, indigestion, and spine misalignment are often related to foot problems. Some runners blow way past this mark: They've logged at least 100,000 in running miles alone. One committed runner, Herb Fred, has run a whopping 247,142 miles.

12. FOOT SIZE HAS ZERO TO DO WITH PENIS SIZE.

In a study published in 2015, researchers synthesized data from 17 previous studies that included the penis measurements of more than 15,000 men from around the world. The results: There is little evidence that penis size is linked to height, body mass, or shoe size.

13. THERE'S A REASON GRANDPA'S TOENAILS LOOK LIKE THAT.

Ever heard someone describing their toenails as “horse hooves”? As we get older, our toenails tend to thicken, making them hard to trim. This happens because toenails grow more slowly as we age, causing the nail cells to accumulate. Stubbing toes, bad shoes, and dropping things on your feet can also cause thickening, as can fungal infections and peripheral arterial disease, which narrows arteries and reduces the blood flow to limbs.

14. THERE'S A GUINNESS WORLD RECORD FOR MOST FEET AND ARMPITS SNIFFED.

Odds are you don’t have any job-related tasks nearly as revolting as this one: In the 15 years that Madeline Albrecht worked for an Ohio lab that tests Dr. Scholl products, she sniffed more than 5600 feet and untold numbers of armpits. Albrecht currently holds the Guinness World Record for—yes, this is a category—the number of feet and armpits sniffed.

11 Insightful Facts About Eyes

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iStock.com/Paffy69

There are a lot of myths and misconceptions about the eyes. No, sitting too close to the TV won't damage your vision, and reading in dim light won’t hurt either. It’s understandable that various parts of the eye are so little understood, though. Each eye has more than a million optic nerve cells and over 106 million photoreceptor cells, making it one of the most complex organs we have. Here are a few more things you should know about your “windows to the soul.”

1. Newborn babies see the world in black and white—and red.

“It is a myth that babies see in black and white,” Anna Franklin, leader of the University of Sussex's Baby Lab, told The Guardian. While newborns do see black, white, and shades of gray, they can also detect red objects against a gray backdrop, Franklin says. The reason why they can’t see more colors is because the cones in their eyes—the photoreceptor cells responsible for picking up colors—are too weak to detect them. Those cells quickly get stronger, though. After about two months, babies can distinguish between red and green, and a few weeks later they can tell the difference between blue and yellow.

2. Your eyeballs grow as you age.

Another common misconception is that your eyes remain the same size from birth to adulthood. As a newborn, your eyes measure about three-fifths of an inch from front to back, compared to a little under an inch in adults. Your eyes actually grow a great deal in the first two years of life, and another growth spurt occurs when you go through puberty. The confusion likely stems from the fact that your eyes as a 6-month-old infant are two-thirds the size they will be when you’re an adult.

3. The length of your eye partly determines how well you'll be able to see.

If your eyeball is too long or too short, you might end up having problems with your vision. Nearsighted people have eyes that are longer than average, while farsighted people have eyes that come up a little short. If you were to magically add or remove a millimeter of length from your eye, it would completely change your prescription. Aside from eye length, the shape of your cornea (the outer part of the eye where contact lenses are placed) and lens (the part of the eye located behind the iris and pupil) are other key factors that determine the quality of your vision. That's because both of these parts work together to refract light.

4. Contact lenses can't really get lost behind your eye.

Although it may feel like a dislodged contact lens is stuck behind your eye, that isn’t exactly what’s happening. The thin membrane covering the white part of your eye and the underside of your eyelid—called the conjunctiva—forms a pouch and prevents objects from getting behind your eyeball. If a contact lens gets shifted out of place to the point where you can no longer see it, it’s just stuck underneath your upper eyelid, which isn’t nearly as scary.

5. Blue-eyed people share a common ancestor.

Originally, everyone in the world had brown eyes. It wasn’t until around 6000 to 10,000 years ago that the first blue-eyed person was born as a result of a genetic mutation, according to a 2008 study. That mutation of the OCA2 gene essentially “turned off the ability to produce brown eyes” and diluted the color to blue, Professor Hans Eiberg of the University of Copenhagen said in a statement.

6. Parts of the eye can get sunburned.

There’s a good reason you should wear sunglasses when it’s bright outside. Too much exposure to UV rays can damage the surface of the cornea and conjunctiva, causing a condition akin to sunburn called photokeratitis. Symptoms include pain, red or swollen eyes, the sensation of a foreign body in the eyes, blurred vision, headaches, and seeing halos around lights. While the discomfort is temporary and tends to go away within 48 hours, longer exposure to UV rays can have a long-term effect on your vision and lead to macular degeneration (deterioration of the retina, which is often age-related) and cataracts (clouding of the eye's lens, which reduces the amount of light coming in).

7. Your eye muscles are the fastest muscle in your body.

Extraocular muscles are what let you look around in all directions. You have six of these muscles in each eye, and many of the motions they make are involuntary. This lets you flick your eyes to one side and notice something in your peripheral vision without consciously looking in that direction. When both of your eyes move in the same direction, the movement is called a saccade, which comes from the French word for “jerk” (the verb, not the person). These jerky movements are extremely rapid, lasting about 50 to 60 milliseconds per saccade, according to Dr. Reza Shadmehr, professor of biomedical engineering and neuroscience at Johns Hopkins University. “Saccadic eye movements are the fastest voluntary movements that we can make. The eyes move at around 500 degrees per second or more,” Shadmehr tells Mental Floss.

8. Your eye movements might give away your next move.

Shadmehr and other researchers conducted an experiment in 2015 to test the relationship between saccades and decision-making. Participants were placed in front of a computer and asked to choose between two options that appeared on the screen: an immediate reward and a delayed reward. For instance, one option might be “get $10 today,” while the other might be “wait 30 days and get $30.” Their eye movements were tracked the entire time, and researchers discovered that these movements gave away the choice they were about to make before they made it. At the last minute, their eyes would move at a faster velocity towards the option that they preferred.

“What’s interesting is that as the saccades are being made, the velocity of the eyes starts out being equal between these two stimuli, but then right before you decide ‘I like A better than B,' the saccade that you make toward A has a higher velocity than the one you make toward B,” Shadmehr explains. “The idea is that the way you’re evaluating things is reflected in the way you move toward them.”

In another experiment, Shadmehr found a correlation between faster eye movements and impatient and impulsive behaviors. Similarly, other studies have shown that our eye movements are linked to moral decisions and even our political temperament.

9. You can tell some animals' place in the food chain by looking at a part of their eye.

In 2015, vision scientist Martin Banks and his colleagues looked at the eyes of 214 species in an attempt to answer the question, “Why do animal eyes have pupils of different shapes?” By the end of their study, they noticed a few patterns. Predatory animals like big cats and snakes tend to have pupils in the shape of vertical slits. This particular shape gives them the advantage of being able to accurately judge the distance separating them and their prey, so they'll know exactly how far they have to pounce. On the other hand, horizontal pupils are more common in goats, deer, cattle, and other herbivores. This shape improves an animal’s panoramic vision, which helps them look out for predators.

10. An eye condition may have been partly responsible for Leonardo da Vinci's artistic genius.

Visual neuroscientist Christopher Tyler argued in a recent paper that the master artist behind Mona Lisa had strabismus, a disorder where the eyes are misaligned. Essentially, one of his eyes turned outwards, and he was able to use both of his eyes separately (monocular as opposed to binocular vision). Tyler believes this actually aided his art by improving his ability to render three-dimensional images on a flat canvas. “The condition is rather convenient for a painter, since viewing the world with one eye allows direct comparison with the flat image being drawn or painted,” Tyler said. We’ll never know for sure whether or not this was true for Leonardo, but it’s an intriguing theory.

11. SURGEONS HOPE TO BE PERFORMING WHOLE EYE TRANSPLANTS BY 2026. 

Currently, only cornea transplants to improve vision are possible, but a team of Pittsburgh-based transplant surgeons said in 2016 that they hoped to be performing whole eye transplants in humans within the next decade. Transferring an eye from a deceased donor to a recipient certainly won’t be easy, though. A complicated network of muscles, blood vessels, and nerves connects the eyes to the brain via the optic nerve. However, further studies into the optic nerve and recent advances in immunosuppressive drugs and surgical techniques have brought them several steps closer to achieving this goal. If successful, the surgery could restore vision to people who have suffered severe eye injuries. Their research is backed by the Department of Defense, which is concerned about the number of soldiers who sustain eye injuries in combat.

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