11 Amazing Facts About Veins

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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.

Beneath your skin, and deeper within your body, run networks of veins. These thin, tube-like structures are an essential part of the circulatory system, which distributes blood and nutrients throughout the body. What Thomas E. Eidson, a phlebologist (vein disease specialist) at Atlas Vein Care in Arlington, Texas, finds most compelling about veins is "how absolutely intricate and fragile the circulatory system can seem and yet at the same time be so resilient and adaptive."

1. VEINS ARE ONE OF THREE KINDS OF BLOOD VESSELS.

Three types of blood vessels make up the human circulatory system: arteries, veins, and capillaries. All three of these vessels transport blood, oxygen, nutrients, and hormones to organs and cells. While arteries carry oxygenated blood away from the heart to the tissues of the body, veins carry oxygen-depleted blood from the tissues back to the heart, and in fact have special valves that help them to achieve this directional flow. Capillaries are tiny blood vessels that connect arteries to veins and allow nutrients in the blood to diffuse to the body's tissues.

2. A SINGLE VEIN IS COMPRISED OF THREE LAYERS.

Veins, small as they are, consist of three layers. According to Eidson, these layers are known as the tunica adventitia, tunica media, and tunica intima. The tunica adventitia is the tough outer layer of arteries and veins and is made mainly of connective tissues. The middle layer, tunica media, is all smooth muscle and elastic fibers. This layer is thinner in veins than in arteries. The innermost layer, tunica intima, comes in direct contact with blood as it flows through the vein. This structure is made up of smooth cells and has a hollow center known as the lumen.

3. OUR BODIES CONTAIN UP TO 100,000 MILES OF BLOOD VESSELS.

All the arteries, veins, and capillaries of a human child, stretched end to end, are estimated to wrap around the Earth about 2.5 times (the equivalent of about 60,000 miles). The amount of blood vessels in a human adult would circle our planet four times, equaling 100,000 miles, according to Eidson.

4. CAPILLARIES ARE SMALLER THAN THE WIDTH OF A HUMAN HAIR.

Capillaries are tiny—at their smallest, they're less than a third of the thickness of a human hair. But to really put it into perspective, consider that when red blood cells flow through capillaries, "[they] must travel through them one cell at a time in a single-file line," Eidson says.

5. PHYSICIANS HAD THE CIRCULATORY SYSTEM ALL WRONG UNTIL THE 17TH CENTURY.

"Physicians followed an incorrect model of the circulatory system proposed by Greek physician and philosopher Galen of Pergamon from about the 2nd century CE until the 1600s," Eidson says. According to a paper in the Journal of Thrombosis and Haemostasis, Galen thought there were two systems: one in which the liver, not the heart, produced blood that was distributed in the body centrifugally, and another where arteries carried air from the lungs and more blood to tissues. "Blood was not seen to circulate but rather to slowly ebb and flow," author W.C. Aird wrote. This attitude prevailed until 1628, when English physician William Harvey first correctly described the circulatory system and the function of the heart.

6. THE BODY CAN FORM NEW VESSELS WHEN ONE IS BLOCKED.

Eidson says the body can form new blood vessels if a pathway gets blocked, a process called angiogenesis or neovascularization. On the positive side, this is the process by which flesh wounds heal, drawing nutrients and oxygen from the nearest healthy capillaries to the site of those that are damaged; this isn't too hard given how numerous capillaries are in the body. On the negative side, this same process can lead to corneal neovascularization, in which new blood vessels invade the cornea from the limbus, a part of the eye where the cornea meets the sclera—the white part of the eye. The extra blood vessels can cause inflammation and scarring of the cornea, and even result in blindness.

7. ONE PHYSICIAN PERFORMED A PIONEERING EXPERIMENT ON VEINS IN THE ARM—HIS OWN.

German physician Werner Forssmann performed a cardiac catheterization on himself in 1929. In this procedure, a thin tube called a catheter is inserted into one of the large blood vessels in the arm that leads to the heart. The medical community at the time believed studying the heart was highly unorthodox, but Forssmann was determined to prove them wrong. If the procedure succeeded, Forssmann would be able to show that a catheter could assess the pressure in the organ and how well the heart is working.

He made an incision on the inside of his left elbow and threaded the thin tube into his heart—and had a technician take an X-ray to prove the penetration was a success. Then he calmly removed the catheter from his arm with no side effects. Now, "it's a procedure performed in the U.S. approximately 1 million times per year," Eidson says. Forssmann also went on to win the Nobel Prize for Medicine in 1956, shutting up his detractors.

8. STRONG VEINS ARE ESSENTIAL TO A STRONG BODY.

Veins return oxygen-depleted blood back to the heart against the force of gravity. "If veins are too weak—a condition called venous insufficiency—blood can pool in the legs and skin causing swelling, pain, discoloration, and wounds," says Albert Malvehy, a venous and lymphatic specialist and phlebology sonographer in Delray Beach, Florida. Chronic venous insufficiency is more common in people who are obese, pregnant, or who have a family history of the problem. It can also be caused by high blood pressure in the leg veins, as a result of sitting or standing for long stints; not enough exercise, smoking, or deep vein thrombosis (blood clots). Depending on the severity, treatments may range from medication to surgery.

9. VARICOSE VEINS ARE CAUSED BY DAMAGED VALVES.

When venous valves are damaged, blood can flow in the wrong direction and lead to stretched-out, bulging veins, Gregory P. Kezele, the medical director of Vein Clinics of Cleveland, tells Mental Floss. Varicose veins, which can range in color from purplish to neutral, appear twisted and gnarled, and may be raised on the skin's surface. (Don't confuse them with spider veins, which are clusters of bluish or reddish veins near the surface of the skin that resemble webs, hence the name.) Conditions like pregnancy, obesity, and genetic predisposition can cause them. Once varicose veins appear—usually on the legs—they require a medical procedure to get rid of them.

Veins are a critical part of normal circulation in the body, so varicose veins can be more than just a cosmetic issue. "They can be a sign of a deeper circulation problem," Malvehy says. "People with varicose veins, leg pain, restless legs syndrome, leg wounds, and leg swelling should be checked by a vein specialist."

One in five people have vein disease. As recently as 10 years ago, there were few treatments to offer varicose vein sufferers except for vein stripping surgery, in which problematic veins are removed. Malvehy says that over the past decade, "there has been a revolution in treatment, such that almost all vein issues can be treated in the office with no downtime."

One common treatment is sclerotherapy, in which a liquid solution is forced into the bulging vein to stop the flow of blood. The vein will eventually turn into scar tissue and fade away, though follow-up treatments might be needed.

Another treatment is thermal ablation, performed using ultrasound guidance. Kezele explains that a physician will insert a small catheter into the diseased veins, which then delivers heat; the heat will close off blood flow to the problem veins and improve circulation as blood diverts to healthy veins.

10. AN EARLY DEPICTION OF VEIN DISEASE APPEARS IN A SCULPTURE FROM 340 BCE.

According to Kezele, the first depiction of vein disease appears on a Greek tablet dating to the 4th century BCE. The carving, from the sanctuary of Amynos, shows a man clutching a giant, disembodied leg with a bulging vein. Kezele suggests on his website that "it shows the Greek official Lysimachides dedicating a fake leg suffering from a varicose vein to Amynos," an Athenian hero revered as a healer.

11. VEINS MIGHT "POP OUT" WHEN YOU EXERCISE.

There are lots of theories on why athletes often have big, bodaciously bulging veins visible on their arms or legs after they work out. The ropy look is completely normal and temporary. Writing in Scientific American, physiology professor Mark A. W. Andrews said that a likely cause of protruding veins is arterial blood pressure during exercise. Blood that would otherwise be resting in capillaries is forced out by the pressure into the surrounding muscle. That process—called filtration—makes the muscles swell, which pushes nearby veins closer to the skin's surface so they take on a bulging appearance. The process is more noticeable in athletes and body builders with very little subcutaneous fat.

12 Creative Ways to Spend Your FSA Money Before the Deadline

stockfour/iStock via Getty Images
stockfour/iStock via Getty Images

If you have a Flexible Spending Account (FSA), chances are, time is running out for you to use that cash. Depending on your employer’s rules, if you don’t spend your FSA money by the end of the grace period, you potentially lose some of it. Lost cash is never a good thing.

For those unfamiliar, an FSA is an employer-sponsored spending account. You deposit pre-tax dollars into the account, and you can spend that money on a number of health care expenses. It’s kind of like a Health Savings Account (HSA), but with a few big differences—namely, your HSA funds roll over from year to year, so there’s no deadline to spend it all. With an FSA, though, most of your funds expire at the end of the year. Bummer.

The good news is: The law allows employers to roll $500 over into the new year and also offer a grace period of up to two and a half months to use that cash (March 15). Depending on your employer, you might not even have that long, though. The deadline is fast approaching for many account holders, so if you have to use your FSA money soon, here are a handful of creative ways to spend it.

1. Buy some new shades.

Head to the optometrist, get an eye prescription, then use your FSA funds to buy some new specs or shades. Contact lenses and solution are also covered.

You can also buy reading glasses with your FSA money, and you don’t even need a prescription.

2. Try acupuncture.

Scientists are divided on the efficacy of acupuncture, but some studies show it’s useful for treating chronic pain, arthritis, and even depression. If you’ve been curious about the treatment, now's a good time to try it: Your FSA money will cover acupuncture sessions in some cases. You can even buy an acupressure mat without a prescription.

If you’d rather go to a chiropractor, your FSA funds cover those visits, too.

3. Stock up on staples.

If you’re running low on standard over-the-counter meds, good news: Most of them are FSA-eligible. This includes headache medicine, pain relievers, antacids, heartburn meds, and anything else your heart (or other parts of your body) desires.

There’s one big caveat, though: Most of these require a prescription in order to be eligible, so you may have to make an appointment with your doctor first. The FSA store tells you which over-the-counter items require a prescription.

4. Treat your feet.

Give your feet a break with a pair of massaging gel shoe inserts. They’re FSA-eligible, along with a few other foot care products, including arch braces, toe cushions, and callus trimmers.

In some cases, foot massagers or circulators may be covered, too. For example, here’s one that’s available via the FSA store, no prescription necessary.

5. Get clear skin.

Yep—acne treatments, toner, and other skin care products are all eligible for FSA spending. Again, most of these require a prescription for reimbursement, but don’t let that deter you. Your doctor is familiar with the rules and you shouldn’t have trouble getting a prescription. And, as WageWorks points out, your prescription also lasts for a year. Check the rules of your FSA plan to see if you need a separate prescription for each item, or if you can include multiple products or drug categories on a single prescription.

While we’re on the topic of faces, lip balm is another great way to spend your FSA funds—and you don’t need a prescription for that. There’s also no prescription necessary for this vibrating face massager.

6. Fill your medicine cabinet.

If your medicine cabinet is getting bare, or you don’t have one to begin with, stock it with a handful of FSA-eligible items. Here are some items that don’t require a prescription:

You can also stock up on first aid kits. You don’t need a prescription to buy those, and many of them come with pain relievers and other medicine.

7. Make sure you’re covered in the bedroom.

Condoms are FSA-eligible, and so are pregnancy tests, monitors, and fertility kits. Female contraceptives are also covered when you have a prescription.

8. Prepare for your upcoming vacation.

If you have a vacation planned this year, use your FSA money to stock up on trip essentials. For example:

9. Get a better night’s sleep.

If you have trouble sleeping, sleep aids are eligible, though you’ll need a prescription. If you want to try a sleep mask, many of them are eligible without a prescription. For example, there’s this relaxing sleep mask and this thermal eye mask.

For those nights you’re sleeping off a cold or flu, a vaporizer can make a big difference, and those are eligible, too (no prescription required). Bed warmers like this one are often covered, too.

Your FSA funds likely cover more than you realize, so if you have to use them up by the deadline, get creative. This list should help you get started, and many drugstores will tell you which items are FSA-eligible when you shop online.

10. Go to the dentist.

While basics like toothpaste and cosmetic procedures like whitening treatments aren’t FSA eligible, most of the expenses you incur at your dentist’s office are. That includes co-pays and deductibles as well as fees for cleanings, x-rays, fillings, and even the cost of braces. There are also some products you can buy over-the-counter without ever visiting the dentist. Some mouthguards that prevent you from grinding your teeth at night are eligible, as are cleaning solutions for retainers and dentures.

11. Try some new gadgets.

If you still have some extra cash to burn, it’s a great time to try some expensive high-tech devices that you’ve been curious about but might not otherwise want to splurge on. The list includes light therapy treatments for acne, vibrating nausea relief bands, electrical stimulation devices for chronic pain, cloud-connected stethoscopes, and smart thermometers.

12. Head to Amazon.

There are plenty of FSA-eligible items available on Amazon, including items for foot health, cold and allergy medication, eye care, and first-aid kits. Find out more details on how to spend your FSA money on Amazon here.

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30 Pungent Facts About Farts

This man is clearly not trying to hide the fact he just passed gas.
This man is clearly not trying to hide the fact he just passed gas.
BrilliantEye/iStock via Getty Images

Whether you openly admit it or desperately try to hide it, it’s an undeniable fact that every living and breathing human being farts. And while passing what you thought was going to be silent gas only to be wrong in certain situations can definitely be embarrassing, there’s something undeniably humorous about flatulence—no matter your age.

If you do love a good fart joke, you’re in good company. The very first recorded joke, which was written by the Sumerians and dates all the way back to 1900 BCE, was about—you guessed it—breaking wind. And some of the world's great thinkers, from William Shakespeare to J.D. Salinger, have slipped a fart joke (or 10) into their work.

In this episode of The List Show, we're sniffing out 30 fascinating facts about farts—from why humans expel gas to how often the average adult squeezes the cheese. You can watch the full episode below.

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