12 Facts About the Liver

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You may not think much of your liver, hidden as it is deep inside your body, but your liver runs a whole lot of functions on your behalf to keep you healthy. Not only is it your largest internal organ, it is in charge of hundreds of different functions ranging from fighting infection, to manufacturing proteins and hormones, and helping clot your blood.

This reddish brown organ has two lobes, on the right and left, and it hangs out just on top of the gallbladder and next to parts of the pancreas and intestines. Your liver and these neighboring organs work as a team to digest and absorb your food. Its main job is to filter the blood that comes from the digestive tract, before it hits the rest of your body. The liver also detoxifies chemicals and metabolizes drugs. As it does so, the liver secretes bile that ends up back in the intestines. The liver also makes proteins important for blood plasma and other functions. With some expert support, here are 12 facts about this underappreciated, hardworking organ.

1. IT HAS A LOT OF JOBS.

The liver is a very complicated organ with a role in nearly every bodily function, according to Nancy Reau, MD, the section chief of hepatology and associate director of organ transplantation at Rush University. Some of its jobs include making and storing energy; producing proteins vital for body function; processing drugs—prescriptions, OTCs, and “drugs of abuse”; and playing a vital role in immune function. “Although it’s hard to quantify all of the liver’s many roles, it is easy to see how sick a person becomes when the liver stops functioning,” says Reau, who is also co-chair of the American Liver Foundation’s medical advisory committee.

2. IT'S THE SECOND BIGGEST ORGAN NEXT TO SKIN.

Your liver weighs about the same as a small Chihuahua, often as much as three pounds [PDF], and is about the size of a football. It's located just beneath your rib cage on the right side of your body. If you could feel it, it would be rubbery to the touch.

3. IT HAS A DUAL IDENTITY.

Organs usually have a job specific to one region of the body. Glands are specialized types of organs that remove substances from the blood, alter or process them, then release them to other parts of the body or eliminate them. In that respect, the liver, which filters your body’s toxins (such as drugs and alcohol) and pushes them out of your body, is also a gland.

4. IT'S A BLOODY ORGAN.

At its fullest, the liver holds approximately 10 percent of the blood in your body, and pumps nearly 1.5 liters through itself per minute.

5. THE FIRST LIVER TRANSPLANT WAS NOT A GREAT SUCCESS.

Back in 1963, when Dr. Thomas E. Starzl performed the first human liver transplant at the University of Colorado Medical School, success was limited due to the wrong kinds of immunosuppressive drugs, with no patient living more than a few weeks. However, only four years later, the expansion of available immunosuppressive drugs made the first successful liver transplant possible.

6. IT'S THE ONLY ORGAN THAT CAN COMPLETELY REGENERATE.

Like Wolverine, the liver has the incredible ability to completely regrow, and it only needs as little as 25 percent of the original tissue to do so. “When a person donates more than half of their liver to someone who needs a transplant, the liver returns to its original size in nearly two weeks,” Reau tells Mental Floss. According to a 2009 study in the Journal of Cell Physiology, evolutionary safeguards are responsible for this regenerative effect due to the numerous functions performed by the liver. “This process allows liver to recover lost mass without jeopardizing viability of the entire organism,” the authors write.

7. GOOD THING, BECAUSE YOUR BRAIN DEPENDS ON A HEALTHY LIVER.

The liver is a major regulator of plasma glucose and ammonia levels. If these get out of control they can contribute to a condition known as hepatic encephalopathy, and eventually coma. In other words, if you want your brain to function, you need a working liver.

8. LIVER CONDITIONS MAY BE SYMPTOMLESS.

Liver conditions are among those that pose a quandary for diagnosis. Because many liver conditions from hepatitis to cirrhosis may have no symptoms in the early stages. “You can even have a serious liver injury when your liver tests are all normal,” says Reau.

9. BEWARE YOUR NATURAL SUPPLEMENTS, TOO.

You may think if an herb or supplement has the word natural on the bottle that it’s safe. However, Reau cautions, “Herbs and all-natural therapy [are] processed by the liver in the same way that FDA-approved medications are processed.” It’s best to talk with your doctor if you’re uncertain. Although liver injury is uncommon for both prescribed and complementary therapies, being “all natural” does not eliminate all risk.

10. YOUR LIVER IS CONCERNED ABOUT YOUR WEIGHT …

Your body needs about one gram (.03 ounces) of liver for every kilogram (35 ounces) of your body weight in order to effectively do its job, Dr. Neil Mukherjee, a liver surgeon and fellow at Florida Hospital's Southeastern Center for Digestive Disorders & Pancreatic Cancer, tells Mental Floss.

11. … AND IT RAISES YOUR BILE.

The liver is a busy brew factory of bile, that yellow, green or brownish fluid you only ever see when you’re greeting the toilet with the stomach flu or a hangover. It produces about 700 to 1000 ml of the stuff every day. The bile gathers in little ducts and then moves on to the main bile duct, where it’s carried to the duodenum of the small intestine, either directly or via the gallbladder. While it may sound gross, bile is key to your body's ability to break down and absorb fats.

12. NO MATTER SHAPE OR SIZE, ALL VERTEBRATES HAVE ONE.

Every vertebrate—that is, any living being that has a spinal cord—has a liver, a necessary part of survival. And, these livers all have a similar structure, performing the same essential tasks in all these bodies.

7 Facts About Blood

Moussa81/iStock via Getty Images
Moussa81/iStock via Getty Images

Everyone knows that when you get cut, you bleed—a result of the constant movement of blood through our bodies. But do you know all of the functions the circulatory system actually performs? Here are some surprising facts about human blood—and a few cringe-worthy theories that preceded the modern scientific understanding of this vital fluid.

1. Doctors still use bloodletting and leeches to treat diseases.

Ancient peoples knew the circulatory system was important to overall health. That may be one reason for bloodletting, the practice of cutting people to “cure” everything from cancer to infections to mental illness. For the better part of two millennia, it persisted as one of the most common medical procedures.

Hippocrates believed that illness was caused by an imbalance of four “humors”—blood, phlegm, black bile, and yellow bile. For centuries, doctors believed balance could be restored by removing excess blood, often by bloodletting or leeches. It didn’t always go so well. George Washington, for example, died soon after his physician treated a sore throat with bloodletting and a series of other agonizing procedures.

By the mid-19th century, bloodletting was on its way out, but it hasn’t completely disappeared. Bloodletting is an effective treatment for some rare conditions like hemochromatosis, a hereditary condition causing your body to absorb too much iron.

Leeches have also made a comeback in medicine. We now know that leech saliva contains substances with anti-inflammatory, antibiotic, and anesthetic properties. It also contains hirudin, an enzyme that prevents clotting. It lets more oxygenated blood into the wound, reducing swelling and helping to rebuild tiny blood vessels so that it can heal faster. That’s why leeches are still sometimes used in treating certain circulatory diseases, arthritis, and skin grafting, and helps reattach fingers and toes. (Contrary to popular belief, even the blood-sucking variety of leech is not all that interested in human blood.)

2. Scientists didn't understand how blood circulation worked until the 17th century.

William Harvey, an English physician, is generally credited with discovering and demonstrating the mechanics of circulation, though his work developed out of the cumulative body of research on the subject over centuries.

The prevailing theory in Harvey’s time was that the lungs, not the heart, moved blood through the body. In part by dissecting living animals and studying their still-beating hearts, Harvey was able to describe how the heart pumped blood through the body and how blood returned to the heart. He also showed how valves in veins helped control the flow of blood through the body. Harvey was ridiculed by many of his contemporaries, but his theories were ultimately vindicated.

3. Blood types were discovered in the early 20th century.

Austrian physician Karl Landsteiner discovered different blood groups in 1901, after he noticed that blood mixed from people with different types would clot. His subsequent research classified types A, B and O. (Later research identified an additional type, AB). Blood types are differentiated by the kinds of antigens—molecules that provoke an immune system reaction—that attach to red blood cells.

People with Type A blood have only A antigens attached to their red cells but have B antigens in their plasma. In those with Type B blood, the location of the antigens is reversed. Type O blood has neither A nor B antigens on red cells, but both are present in the plasma. And finally, Type AB has both A and B antigens on red cells but neither in plasma. But wait, there’s more! When a third antigen, called the Rh factor, is present, the blood type is classified as positive. When Rh factor is absent, the blood type is negative.

Scientists still don’t understand why humans have different blood types, but knowing yours is important: Some people have life-threatening reactions if they receive a blood type during a transfusion that doesn’t “mix” with their own. Before researchers developed reliable ways to detect blood types, that tended to turn out badly for people receiving an incompatible human (or animal!) blood transfusion.

4. Blood makes up about 8 percent of our total body weight.

Adult bodies contain about 5 liters (5.3 quarts) of blood. An exception is pregnant women, whose bodies can produce about 50 percent more blood to nourish a fetus.)

Plasma, the liquid portion of blood, accounts for about 3 liters. It carries red and white blood cells and platelets, which deliver oxygen to our cells, fight disease, and repair damaged vessels. These cells are joined by electrolytes, antibodies, vitamins, proteins, and other nutrients required to maintain all the other cells in the body.

5. A healthy red blood cell lasts for roughly 120 days.

Red blood cells contain an important protein called hemoglobin that delivers oxygen to all the other cells in our bodies. It also carries carbon dioxide from those cells back to the lungs.

Red blood cells are produced in bone marrow, but not everyone produces healthy ones. People with sickle cell anemia, a hereditary condition, develop malformed red blood cells that get stuck in blood vessels. These blood cells last about 10 to 20 days, which leads to a chronic shortage of red blood cells, often causing to pain, infection, and organ damage.

6. Blood might play a role in treating Alzheimer's disease.

In 2014, research led by Stanford University scientists found that injecting the plasma of young mice into older mice improved memory and learning. Their findings follow years of experiments in which scientists surgically joined the circulatory systems of old and young mice to test whether young blood could reverse signs of aging. Those results showed rejuvenating effects of a particular blood protein on the organs of older mice.

The Stanford team’s findings that young blood had positive effects on mouse memory and learning sparked intense interest in whether it could eventually lead to new treatments for Alzheimer’s disease and other age-related conditions.

7. The sight of blood can make people faint.

For 3 to 4 percent of people, squeamishness associated with blood, injury, or invasive medical procedures like injections rises to the level of a true phobia called blood injury injection phobia (BII). And most sufferers share a common reaction: fainting.

Most phobias cause an increase in heart rate and blood pressure, and often muscle tension, shakes, and sweating: part of the body’s sympathetic nervous system’s “fight or flight” response. But sufferers of BII experience an added symptom. After initially increasing, their blood pressure and heart rate will abruptly drop.

This reaction is caused by the vagus nerve, which works to keep a steady heart rate, among other things. But the vagus nerve sometimes overdoes it, pushing blood pressure and heart rate too low. (You may have experienced this phenomenon if you’ve ever felt faint while hungry, dehydrated, startled, or standing up too fast.) For people with BII, the vasovagal response can happen at the mere sight or suggestion of blood, needles, or bodily injury, making even a routine medical or dental checkup cause for dread and embarrassment.

What Purpose Does the Belly Button Serve?

misuma/iStock via Getty Images
misuma/iStock via Getty Images

While your eyelashes are protecting your eyes, your lungs are letting you breathe, and virtually every other part of your body—inside and out—is performing its own relatively well-known task, your belly button is just sitting there collecting lint. And while it’s true that your navel served its most important purpose before you were born, it’s not totally useless now.

According to ZME Science, back when you were a fetus, your belly button was more of a belly portal: Your umbilical cord extended from it and connected you to the placenta on your mother’s uterine wall. That way, the placenta could channel nutrients and oxygen to you through the cord, and you could send back waste.

Your umbilical cord was cut when you were born, creating a tiny bulge that left behind some scar tissue after it healed. That scar tissue is your belly button, navel, or umbilicus. Though you may have heard that the shape of your belly button is a direct result of the scissor skills of the doctor who delivered you, that’s not true. Dr. Dan Polk, a neonatologist in the Chicago area, told the Chicago Tribune that a belly button's shape “has to do with how much baby skin leads onto the umbilical cord from the baby’s body. Less skin makes an innie; more skin makes an outie.” About 90 percent of people have innies.

Regardless of how your belly button looks, you probably don’t use it on a daily basis. However, if you’ve studied anatomy, medicine, or a related field, you might recognize it as the central point by which the abdomen is divided into the following quadrants: right upper, left upper, right lower, and left lower. Another way of classifying that area is into nine regions—including the hypochondriac, lumbar, iliac, epigastric, and hypogastric regions—with the umbilical region at the very center.

Abdominopelvic regions diagram
Blausen Medical, Wikimedia Commons // CC BY 3.0

Your belly button can also serve as the opening for laparoscopic surgery, which can save you from having a scar elsewhere on your abdomen.

The navel is a great central landmark outside of medicine, too. If you’ve taken yoga or Pilates classes, you may have heard it referred to as the center of balance or center of gravity. Because it sits right on top of your abdominal muscles, your belly button is an easy marker for your instructor to mention when they want you to access your core, which helps you balance.

And, of course, belly buttons are notorious for storing quite a bit of lint, which always seems to be blue (you can learn more about that here).

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

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