11 Facts About the Kidneys

iStock.com/Davizro
iStock.com/Davizro

Kidneys are kind of like the Brita filters of the human body. Each of these bean-shaped organs is only about the size of a fist, but they serve several vital functions. In addition to ridding your body of waste, the kidneys also help make red blood cells and regulate your blood pressure. If they aren’t kept healthy, though, they can cause a variety of kidney disease symptoms, from kidney stones to infections that could require a kidney transplant. Here are 11 facts you might not know.

1. Your pair of kidneys is lopsided.

Kidneys are located in the lower back—right below the rib cage—and they’re usually asymmetrical. Your right kidney tends to be smaller and sit a little lower than your left one because it needs to make room for the liver, whose bulkiest part is situated on the right side of your body. Your left kidney, on the other hand, has some more room to sprawl out below the spleen, an organ of smaller stature.

2. There’s a reason why you only need one kidney to live.

Most people have two kidneys at birth, but only one kidney is needed to lead a healthy life. Each kidney has about 1.5 million blood-filtering units called nephrons, which help remove a waste product called urea from blood as it flows through the organs. People only need a minimum of 300,000 nephrons to filter blood properly, and one kidney is more than enough to fulfill this purpose. (People without healthy kidneys can survive with dialysis, a process where blood is filtered by machine, or opt for a kidney transplant.)

3. Your kidneys filter about 45 gallons of blood per day.

Although the heart is responsible for pumping blood throughout the body, the kidneys are doing their fair share of work, too. They filter a half-cup of blood every minute, which works out to be 45 gallons of blood per day—or enough to fill a small bathtub.

4. Kidneys make pee.

As part of the body’s urinary system, kidneys create urine from urea, water, and other waste products. The fluid flows from the kidney’s tubules, which are found inside the nephrons, to two tubes called ureters. The ureters then release the urine into the bladder—and you know what happens from there. But if problems occur, the urine can get backed up and cause kidney infections. In addition, in cases where minerals in the urine crystallize, kidney stones can form.

5. Ancient Egyptians may have been the first people to describe kidneys.

Prior to 2018, it was commonly thought that ancient Egyptians had no knowledge of the kidneys, even though their understanding of medicine and the human body was advanced in other ways. That changed when an Egyptian papyrus dating back some 3500 years revealed otherwise. It contained the world’s first known description of the kidneys, among other medical insights.

6. Kidneys are mentioned frequently in the Bible.

The kidneys are cited more than 30 times in the Bible—far more frequently than the heart, which was rarely mentioned. According to a 2005 article in the Journal of the American Society of Nephrology by Baylor College of Medicine professor Garabed Eknoyan, it was not uncommon for symbolic meaning to be ascribed to various organs in ancient Middle Eastern texts. “Unlike most ancient literature, however, the kidneys receive special attention in the Bible as the seat of conscience, emotions, desire, and wisdom,” Eknoyan wrote. “The broader region of the loins, which according to the Oxford English Dictionary is implied in the now archaic term ‘reins,’ is considered the site of physical strength and prowess.”

7. A procedure for removing kidney stones used to be deadly.

These days, if a patient is unable to pass a kidney stone naturally (albeit painfully), laser and high-frequency sound wave treatments can be used to break the hard mineral deposits into smaller pieces. For much of history, though, a patient’s only option was to go under the knife. Kidney stone surgeries were common from the 16th to 18th centuries, and one of the procedures involved cutting open the perineum, inserting a cutting instrument into the bladder, and chopping up the stone manually. Self-taught surgeon Frère Jacques Beaulieu came up with this technique, but it wasn’t without serious risk. In 1698, 25 of the 60 patients he operated on died.

8. A Dutch doctor used sausage casing, orange juice cans, and a washing machine to invent an "artificial kidney" that predated dialysis.

At the start of World War II, not long after Germany invaded the Netherlands, Dutch doctor Willem Kolff got to work inventing an artificial kidney that evolved into modern-day dialysis. Because supplies were limited during the war, he wrapped semipermeable sausage casings around a wooden drum to create his kidney machine. A patient’s blood was pumped into the casings, and the drum was rotated to remove impurities. Later, he improved his invention by adding orange juice cans and a washing machine to the mix. Some of his earliest patients with kidney failure died after a few days, but in 1945, one woman lived seven more years thanks to Kolff’s machine. When Kolff wasn’t busy creating artificial organs, he was saving lives in other ways: He also established Europe’s first blood blank and helped more than 800 people avoid Nazi concentration camps by hiding them in his hospital.

9. Drinking too much water can be bad for kidneys.

Staying hydrated helps keep your kidneys in good working order, but on the flip side, you don’t want to drink too much water. Doing so can cause a condition called hyponatremia, which occurs when the sodium in the blood becomes diluted because the kidneys can’t get rid of the fluid fast enough. The condition can be severe, causing swelling of the cells. It's uncommon, though, and it mainly occurs among athletes who overexert their bodies and drink extra water to compensate. So how much water is the right amount? It varies from person to person, but the Health and Medicine Division of the National Academies of Sciences, Engineering, and Medicine suggests that women drink around 9 cups (2.2 liters) per day, and that men drink about 13 cups (3 liters).

10. Too much ibuprofen and aspirin can also harm kidneys.

All drugs pass through your kidneys, so you want to be careful what you’re feeding them. If used daily for long periods of time, pain medications like ibuprofen, higher-dose aspirin, and naproxen (Aleve) can damage kidneys and potentially cause a disease called chronic interstitial nephritis. However, taking a daily low-dose aspirin to prevent heart attacks has no effect on kidney function.

11. Climate change may be causing an uptick in chronic kidney disease.

Recent research shows that chronic kidney disease is becoming more prevalent in Central America and parts of Asia, especially among manual laborers who spend most of their day outdoors. Although diabetes and high blood pressure are the main causes of impaired kidney function, these factors were ruled out among workers in El Salvador, Sri Lanka, India, and other countries. Other environmental factors may be involved, but researchers say the extreme heat is largely to blame—and climate change is only making it worse. For one, the more someone sweats, the more dehydrated they become. Over time, this can result in severe kidney damage.

“This can be considered the first disease that’s related to climate change,” Dr. Roberto Lucchini, an environmental medicine and public health professor at Mount Sinai’s Icahn School of Medicine in New York City, tells Mental Floss. He says the problem is so severe in Guatemala that job applicants’ creatinine levels are tested before they’re hired to work an outdoor job. Creatinine is a waste product that gets removed from blood by the kidneys, and if those levels are too high, it could signal a greater risk of kidney disease. Two other studies suggest the problem is even starting to affect outdoor workers in warmer parts of the U.S., including California and Florida. “If this continues as a general trend towards increased temperature, this is concerning,” Lucchini says.

10 Facts About Your Tonsils

iStock/Neustockimages
iStock/Neustockimages

Most of us only become aware of our tonsils if they become swollen or infected. But these masses of lymphatic tissue in the mouth and throat are important immunological gatekeepers at the start of the airways and digestive tract, grabbing pathogens and warding off diseases before they reach the rest of your body. Here are some essential answers about these often-overlooked tissues—like what to do when your tonsils are swollen, and whether you should get your tonsils removed.

1. People actually have four kinds of tonsils.

The term tonsils usually refers to your palatine tonsils, the ones that can be seen at the back of your throat. But tonsillar tissue also includes the lingual tonsil (located in the base of the tongue), tubal tonsils, and the adenoid tonsil (often just called adenoids). "Collectively, these are referred to as Waldeyer's ring," says Raja Seethala, the director of head and neck pathology at the University of Pittsburgh Medical Center and a member of the College of American Pathologists Cancer Committee.

2. Tonsils are one of the body's first responders to pathogens.

The tonsils are a key barrier to inhaled or ingested pathogens that can cause infection or other harm, Seethala tells Mental Floss. "These pathogens bind to specialized immune cells in the lining—epithelium—to elicit an immune response in the lymphoid T and B cells of the tonsil," he says. Essentially, they help jumpstart your immune response.

3. Adenoid tonsils can obstruct breathing and cause facial deformities.

If the adenoid tonsils are swollen, they can block breathing and clog up your sinus drainage, which can cause sinus and ear infections. If adenoids are too big, it forces a person to breathe through their mouth. In children, frequent mouth breathing has the potential to cause facial deformities by stressing developing facial bones. "If the tonsils are too large and cause airway obstruction, snoring, or obstructive sleep apnea, then removal is important," says Donald Levine, an ear, nose, and throat specialist in Nyack, New York. Fortunately, the adenoids tend to get smaller naturally in adulthood.

4. As many of us know, sometimes tonsils are removed.

Even though your tonsils are part of your immune system, Levine tells Mental Floss, "when they become obstructive or chronically infected, then they need to be removed." The rest of your immune system steps in to handle further attacks by pathogens. Another reason to remove tonsils besides size, Levine says, is "chronic tonsillitis due to the failure of the immune system to remove residual bacteria from the tonsils, despite multiple antibiotic therapies."

5. Tonsillectomies have been performed for thousands of years ...

Tonsil removal is believed to have been a phenomenon for three millennia. The procedure is found in ancient Ayurvedic texts, says Seethala, "making it one of the older documented surgical procedures." But though the scientific understanding of the surgery has changed dramatically since then, "the benefits versus harm of tonsillectomy have been continually debated over the centuries," he says.

6. ... and they were probably quite painful.

The first known reported case of tonsillectomy surgery, according to a 2006 paper in Otorhinolaryngology, is by Cornélio Celsus, a Roman "encylopaediest" and dabbler in medicine, who authored a medical encyclopedia titled Of Medicine in the 1st century BCE. Thanks to his work, we can surmise that a tonsillectomy probably was an agonizing procedure for the patient: "Celsus applied a mixture of vinegar and milk in the surgical specimen to hemostasis [stanch bleeding] and also described his difficulty doing that due to lack of proper anesthesia."

7. Tonsil removal was performed for unlikely reasons.

The same paper reveals that among some of the more outlandish reasons for removing tonsils were conditions like "night enuresis (bed-wetting), convulsions, laryngeal stridor, hoarseness, chronic bronchitis, and asthma."

8. An early treatment for swollen tonsils included frog fat.

As early practitioners struggled to perfect techniques for removing tonsils effectively, another early physician, Aetius de Amida, recommended "ointment, oils, and corrosive formulas with frog fat to treat infections."

9. Modern tonsillectomy is much more sophisticated.

A common technique today for removing the tonsils, according to Levine, is a far cry from the painful early attempts. Under brief general anesthesia, Levine uses a process called coblation. "[It's] a kind of cold cautery, so there is almost no bleeding, less post operative pain, and quicker healing. You can return to normal activities 10 days later," Levine says.

10. Sexually-transmitted HPV can cause tonsil cancer.

The incidence of tonsillar cancers is increasing, according to Seethala. "Unlike other head and neck cancers, which are commonly associated with smoking and alcohol, tonsillar cancers are driven by high-risk human papillomavirus (HPV)," he says. "HPV-related tonsillar cancer can be considered sexually transmitted."

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.

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