CLOSE
iStock
iStock

12 Bilious Facts About the Liver

iStock
iStock

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.

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.

nextArticle.image_alt|e
iStock
arrow
science
Why Is Your First Instinct After Hurting Your Finger to Put It in Your Mouth?
iStock
iStock

If you close your fingers in a car door or slam your funny bone into a wall, you might find your first reaction is to suck on your fingers or rub your elbow. Not only is this an instinctive self-soothing behavior, it's a pretty effective technique for temporarily calming pain signals to the brain.

But how and why does it work? To understand, you need to know about the dominant theory of how pain is communicated in the body.

In the 17th century, French scientist and philosopher René Descartes proposed that there were specific pain receptors in the body that "rang a bell in the brain" when a stimulus interacted with the body, Lorne Mendell, a professor of neurobiology and behavior at Stony Brook University in New York, tells Mental Floss. However, no study has effectively been able to identify receptors anywhere in the body that only respond to painful stimuli.

"You can activate certain nerve fibers that can lead to pain, but under other circumstances, they don't," Mendell says. In other words, the same nerve fibers that carry pain signals also carry other sensations.

In 1965, two researchers at MIT, Patrick Wall and Ronald Melzack, proposed what they called the gate control theory of pain, which, for the most part, holds up to this day. Mendell, whose research focuses on the neurobiology of pain and who worked with both men on their pain studies, explains that their research showed that feeling pain is more about a balance of stimuli on the different types of nerve fibers.

"The idea was that certain fibers that increased the input were ones that opened the gate, and the ones that reduced the input closed the gate," Mendell says. "So you have this idea of a gate control sitting across the entrance of the spinal cord, and that could either be open and produce pain, or the gate could be shut and reduce pain."

The gate control theory was fleshed out in 1996 when neurophysiologist Edward Perl discovered that cells contain nociceptors, which are neurons that signal the presence of tissue-damaging stimuli or the existence of tissue damage.

Of the two main types of nerve fibers—large and small—the large fibers carry non-nociceptive information (no pain), while small fibers transmit nociceptive information (pain).

Mendell explains that in studies where electric stimulation is applied to nerves, as the current is raised, the first fibers to be stimulated are the largest ones. As the intensity of the stimulus increases, smaller and smaller fibers get recruited in. "When you do this in a patient at low intensity, the patient will recognize the stimulus, but it will not be painful," he says. "But when you increase the intensity of the stimulus, eventually you reach threshold where suddenly the patient will say, 'This is painful.'"

Thus, "the idea was that shutting the gate was something that the large fibers produced, and opening the gate was something that the small fibers produced."

Now back to your pain. When you suck on a jammed finger or rub a banged shin, you're stimulating the large fibers with "counter irritation," Mendell says. The effect is "a decrease in the message, or the magnitude of the barrage of signals being driven across the incoming fiber activation. You basically shut the gate. That is what reduces pain."

This concept has created "a big industry" around treating pain with mild electrical stimulation, Mendell says, with the goal of stimulating those large fibers in the hopes they will shut the gate on the pain signals from the small fibers.

While counter irritation may not help dull the pain of serious injury, it may come in handy the next time you experience a bad bruise or a stubbed toe.

nextArticle.image_alt|e
The American Museum of Natural History
arrow
Lists
10 Surprising Ways Senses Shape Perception
The American Museum of Natural History
The American Museum of Natural History

Every bit of information we know about the world we gathered with one of our five senses. But even with perfect pitch or 20/20 vision, our perceptions don’t always reflect an accurate picture of our surroundings. Our brain is constantly filling in gaps and taking shortcuts, which can result in some pretty wild illusions.

That’s the subject of “Our Senses: An Immersive Experience,” a new exhibition at the American Museum of Natural History in New York City. Mental Floss recently took a tour of the sensory funhouse to learn more about how the brain and the senses interact.

1. LIGHTING REVEALS HIDDEN IMAGES.

Woman and child looking at pictures on a wall

Under normal lighting, the walls of the first room of “Our Senses” look like abstract art. But when the lights change color, hidden illustrations are revealed. The three lights—blue, red, and green—used in the room activate the three cone cells in our eyes, and each color highlights a different set of animal illustrations, giving the viewers the impression of switching between three separate rooms while standing still.

2. CERTAIN SOUNDS TAKE PRIORITY ...

We can “hear” many different sounds at once, but we can only listen to a couple at a time. The AMNH exhibit demonstrates this with an audio collage of competing recordings. Our ears automatically pick out noises we’re conditioned to react to, like an ambulance siren or a baby’s cry. Other sounds, like individual voices and musical instruments, require more effort to detect.

3. ... AS DO CERTAIN IMAGES.

When looking at a painting, most people’s eyes are drawn to the same spots. The first things we look for in an image are human faces. So after staring at an artwork for five seconds, you may be able to say how many people are in it and what they look like, but would likely come up short when asked to list the inanimate object in the scene.

4. PAST IMAGES AFFECT PRESENT PERCEPTION.

Our senses often are more suggestible than we would like. Check out the video above. After seeing the first sequence of animal drawings, do you see a rat or a man’s face in the last image? The answer is likely a rat. Now watch the next round—after being shown pictures of faces, you might see a man’s face instead even though the final image hasn’t changed.

5. COLOR INFLUENCES TASTE ...

Every cooking show you’ve watched is right—presentation really is important. One look at something can dictate your expectations for how it should taste. Researchers have found that we perceive red food and drinks to taste sweeter and green food and drinks to taste less sweet regardless of chemical composition. Even the color of the cup we drink from can influence our perception of taste.

6. ... AND SO DOES SOUND

Sight isn’t the only sense that plays a part in how we taste. According to one study, listening to crunching noises while snacking on chips makes them taste fresher. Remember that trick before tossing out a bag of stale junk food.

7. BEING HYPER-FOCUSED HAS DRAWBACKS.

Have you ever been so focused on something that the world around you seemed to disappear? If you can’t recall the feeling, watch the video above. The instructions say to keep track of every time a ball is passed. If you’re totally absorbed, you may not notice anything peculiar, but watch it a second time without paying attention to anything in particular and you’ll see a person in a gorilla suit walk into the middle of the screen. The phenomenon that allows us to tune out big details like this is called selective attention. If you devote all your mental energy to one task, your brain puts up blinders that block out irrelevant information without you realizing it.

8. THINGS GET WEIRD WHEN SENSES CONTRADICT EACH OTHER.

Girl standing in optical illusion room.

The most mind-bending room in the "Our Senses" exhibit is practically empty. The illusion comes from the black grid pattern painted onto the white wall in such a way that straight planes appear to curve. The shapes tell our eyes we’re walking on uneven ground while our inner ear tells us the floor is stable. It’s like getting seasick in reverse: This conflicting sensory information can make us feel dizzy and even nauseous.

9. WE SEE SHADOWS THAT AREN’T THERE.

If our brains didn’t know how to adjust for lighting, we’d see every shadow as part of the object it falls on. But we can recognize that the half of a street that’s covered in shade isn’t actually darker in color than the half that sits in the sun. It’s a pretty useful adaptation—except when it’s hijacked for optical illusions. Look at the image above: The squares marked A and B are actually the same shade of gray. Because the pillar appears to cast a shadow over square B, our brain assumes it’s really lighter in color than what we’re shown.

10. WE SEE FACES EVERYWHERE.

The human brain is really good at recognizing human faces—so good it can make us see things that aren’t there. This is apparent in the Einstein hollow head illusion. When looking at the mold of Albert Einstein’s face straight on, the features appear to pop out rather than sink in. Our brain knows we’re looking at something similar to a human face, and it knows what human faces are shaped like, so it automatically corrects the image that it’s given.

All images courtesy of the American Museum of Natural History unless otherwise noted.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios