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.

‘Water’ in Kansas City Woman’s Ear Turned Out to Be a Venomous Brown Recluse Spider

N-sky/iStock via Getty Images
N-sky/iStock via Getty Images

Susie Torres, a resident of Kansas City, Missouri, woke up on Tuesday morning with the distinct feeling that water was lodged in her left ear. She likened it to the swooshing sensation that can often happen after swimming, WDAF-TV reports.

Instead of waiting for the problem to resolve itself, Torres went to the doctor—a decision that might have saved her from some serious pain. The medical assistant was the first to realize something was alarmingly amiss, and immediately called for backup.

“She ran out and said ‘I’m going to get a couple more people,’” Torres told 41 Action News. “She then said, ‘I think you have an insect in there.’” For many people, the thought of having any live insect stuck in an ear would be enough to cue a small- or large-scale freak-out, but Torres stayed calm.

The doctors “had a few tools and worked their magic and got it out,” Torres said. The “it” in question turned out to be a spider—and not just any harmless house spider (which you shouldn’t kill, by the way). It was a venomous brown recluse spider.

“Gross,” Torres told WDAF-TV. “Why, where, what, and how.”

Miraculously, the spider didn’t bite Torres. If it had, she would’ve ended up visiting the doctor with more than general ear discomfort: Brown recluse bites can cause pain, burning, fever, nausea, and purple or blue discoloration of the surrounding skin, according to Healthline.

Torres may have remained admirably level-headed throughout the ordeal, but that doesn’t mean she’s taking it lightly. “I went and put some cotton balls in my ears last night,” she told WDAF-TV. “I’m shaking off my clothes, and I don’t put my purse on the floor. I’m a little more cautious.”

Is this the first time an insect has posted up in the ear of an unsuspecting, innocent human? Absolutely not—here are six more horror stories, featuring a cockroach, a bed bug, and more.

[h/t WDAF-TV]

12 Fantastic Facts About the Immune System

monkeybusinessimages/iStock via Getty Images
monkeybusinessimages/iStock via Getty Images

If it weren't for our immune system, none of us would live very long. Not only does the immune system protect us from external pathogens like viruses, bacteria, and parasites, but it also battles cells that have mutated due to illnesses, like cancer, within the body. Here are 12 fascinating facts about the immune system.

1. The immune system saves lives.

The immune system is a complex network of tissues and organs that spreads throughout the entire body. In a nutshell, it works like this: A series of "sensors" within the system detects an intruding pathogen, like bacteria or a virus. Then the sensors signal other parts of the system to kill the pathogen and eliminate the infection.

"The immune system is being bombarded by all sorts of microbes all the time," Russell Vance, professor of immunology at University of California, Berkeley and an investigator for the Howard Hughes Medical Institute, tells Mental Floss. "Yet, even though we're not aware of it, it's saving our lives every day, and doing a remarkably good job of it."

2. Before scientists understood the immune system, illness was chalked up to unbalanced humors.

Long before physicians realized how invisible pathogens interacted with the body's system for fighting them off, doctors diagnosed all ills of the body and the mind according to the balance of "four humors": melancholic, phlegmatic, choleric, or sanguine. These criteria, devised by the Greek philosopher Hippocrates, were divided between the four elements, which were linked to bodily fluids (a.k.a. humors): earth (black bile), air (blood), water (phlegm) and fire (yellow bile), which also carried properties of cold, hot, moist, or dry. Through a combination of guesswork and observation, physicians would diagnose patients' humors and prescribe treatment that most likely did little to support the immune system's ability to resist infection.

3. Two men who unraveled the immune system's functions were bitter rivals.

Two scientists who discovered key functions of the immune system, Louis Pasteur and Robert Koch, should have been able to see their work as complementary, but they wound up rivals. Pasteur, a French microbiologist, was famous for his experiments demonstrating the mechanism of vaccines using weakened versions of the microbes. Koch, a German physician, established four essential conditions under which pathogenic bacteria can infect hosts, and used them to identify the Mycobacterium tuberculosis bacterium that causes tuberculosis. Though both helped establish the germ theory of disease—one of the foundations of modern medicine today—Pasteur and Koch's feud may have been aggravated by nationalism, a language barrier, criticisms of each other's work, and possibly a hint of jealousy.

4. Specialized blood cells are the immune system's greatest weapon.

The most powerful weapons in your immune system's arsenal are white blood cells, divided into two main types: lymphocytes, which create antigens for specific pathogens and kill them or escort them out of the body; and phagocytes, which ingest harmful bacteria. White blood cells not only attack foreign pathogens, but recognize these interlopers the next time they meet them and respond more quickly. Many of these immune cells are produced in your bone marrow but also in the spleen, lymph nodes, and thymus, and are stored in some of these tissues and other areas of the body. In the lymph nodes, which are located throughout your body but most noticeably in your armpits, throat, and groin, lymphatic fluid containing white blood cells flows through vein-like tubules to escort foreign invaders out.

5. The spleen helps your immune system work.

Though you can live without the spleen, an organ that lies between stomach and diaphragm, it's better to hang onto it for your immune function. According to Adriana Medina, a doctor who specializes in hematology and oncology at the Alvin and Lois Lapidus Cancer Institute at Sinai Hospital in Baltimore, your spleen is "one big lymph node" that makes new white blood cells and cleans out old blood cells from the body.

It's also a place where immune cells congregate. "Because the immune cells are spread out through the body," Vance says, "eventually they need to communicate with each other." They do so in both the spleen and lymph nodes.

6. You have immune cells in all of your tissues.

While immune cells may congregate more in lymph nodes than elsewhere, "every tissue in your body has immune cells stationed in it or circulating through it, constantly roving for signs of attack," Vance explains. These cells also circulate through the blood. The reason for their widespread presence is that there are thousands of different pathogens that might infect us, from bacteria to viruses to parasites. "To eliminate each of those different kinds of threats requires specialized detectors," he says.

7. How friendly you're feeling could be linked to your immune system.

From an evolutionary perspective, humans' high sociability may have less to do with our bigger brains, and more to do with our immune system's exposure to a greater number of bacteria and other pathogens.

Researchers at the University of Virginia School of Medicine have theorized that interferon gamma (IG), a substance that helps the immune system fight invaders, was linked to social behavior, which is one of the ways we become exposed to pathogens.

In mice, they found IG acted as a kind of brake to the brain's prefrontal cortex, essentially stopping aberrant hyperactivity that can cause negative changes in social behavior. When they blocked the IG molecule, the mice's prefrontal cortexes became hyperactive, resulting in less sociability. When they restored the function, the mice's brains returned to normal, as did their social behavior.

8. Your immune system might recruit unlikely organs, like the appendix, into service.

The appendix gets a bad rap as a vestigial organ that does nothing but occasionally go septic and create a need for immediate surgery. But the appendix may help keep your gut in good shape. According to Gabrielle Belz, professor of molecular immunology at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, research by Duke University's Randal Bollinger and Bill Parker suggests the appendix houses symbiotic bacteria that are important for overall gut health—especially after infections wipe out the gut's good microbes. Special immune cells known as innate lymphoid cells (ILCs) in the appendix may help to repopulate the gut with healthy bacteria and put the gut back on track to recovery.

9. Gut bacteria has been shown to boost immune systems in mice.

Researchers at the University of Chicago noticed that one group of mice in their lab had a stronger response to a cancer treatment than other mice. They eventually traced the reason to a strain of bacteria—Bifidobacterium—in the mice's guts that boosted the animals' immune system to such a degree they could compare it to anti-cancer drugs called checkpoint inhibitors, which keep the immune system from overreacting.

To test their theory, they transferred fecal matter from the robust mice to the stomachs of less immune-strengthened mice, with positive results: The treated mice mounted stronger immune responses and tumor growth slowed. When they compared the bacterial transfer effects with the effects of a checkpoint inhibitor drug, they found that the bacteria treatment was just as effective. The researchers believe that, with further study, the same effect could be seen in human cancer patients.

10. Scientists are trying to harness the immune system's "Pac-Man" cells to treat cancer.

Aggressive pediatric tumors are difficult to treat due to the toxicity of chemotherapy, but some researchers are hoping to develop effective treatments without the harmful side effects. Stanford researchers designed a study around a recently discovered molecule known as CD47, a protein expressed on the surface of all cells, and how it interacts with macrophages, white blood cells that kill abnormal cells. "Think of the macrophages as the Pac-Man of the immune system," Samuel Cheshier, lead study author and assistant professor of neurosurgery at Stanford Medicine, tells Mental Floss.

CD47 sends the immune system's macrophages a "don't eat me" signal. Cancer cells fool the immune system into not destroying them by secreting high amounts of CD47. When Cheshier and his team blocked the CD47 signals on cancer cells, the macrophages could identify the cancer cells and eat them, without toxic side effects to healthy cells. The treatment successfully shrank all five of the common pediatric tumors, without the nasty side effects of chemotherapy.

11. A new therapy for type 1 diabetes tricks the immune system.

In those with type 1 diabetes, the body attacks its own pancreatic cells, interrupting its normal ability to produce insulin in response to glucose. In a 2016 paper, researchers at MIT, in collaboration with Boston's Children's Hospital, successfully designed a new material that allows them to encapsulate and transplant healthy pancreatic "islet" cells into diabetic mice without triggering an immune response. Made from seaweed, the substance is benign enough that the body doesn't react to it, and porous enough to allow the islet cells to be placed in the abdomen of mice, where they restore the pancreatic function. Senior author Daniel Anderson, an associate professor at MIT, said in a statement that this approach "has the potential to provide [human] diabetics with a new pancreas that is protected from the immune system, which would allow them to control their blood sugar without taking drugs. That's the dream."

12. Immunotherapy is on the cutting edge of immune system research.

Over the last few years, research in the field of immunology has focused on developing cancer treatments using immunotherapy. This method engineers the patient's own normal cells to attack the cancer cells. Vance says the technique could be used for many more conditions. "I feel like that could be just the tip of the iceberg," he says. "If we can understand better what the cancer and immunotherapy is showing, maybe we can go in there and manipulate the immune responses and get good outcomes for other diseases, too."

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