Scientists May Have Just Discovered a New Organ—And It Could Be the Biggest Yet

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A new study published in Scientific Reports boldly proclaims that researchers from NYU School of Medicine and Mount Sinai Beth Israel Medical Center, both in New York City, have identified a new organ in the body, thought to be the biggest organ of them all. Called "the interstitium," what has long been thought to be merely tough, dense connective tissue running throughout the body—beneath the skin, the visceral organs, around arteries and veins, and in the fascia tissue between muscles—is really a network of fluid-filled compartments whose structure easily defies viewing by traditional methods, the researchers say.

When asked how researchers can call something found in numerous parts of the body an organ, Neil Theise, co-author of the study, and professor of pathology at NYU School of Medicine, tells Mental Floss that it satisfied both definitions of an organ, being "a tissue that is unitary in structure" that has "a unitary set of functions." It might more accurately be called "an organ system" similar to the cardiovascular system and the lymphatic system.

In all of the places that it's found, the interstitium's fluid-filled compartments (which are the source of lymph, a fluid central to immune cell function) are surrounded by bundles of collagen and elastin—strong and flexible connective tissues that seem to form a sturdy framework for the compartments.

They have the "same cell types, same sort of structure [and] architecture, and the same relationship with the lymphatic system wherever they're found," Theise says. This makes sense, because the compartments drain directly into the lymphatic system. This might explain why cancer cells that get into the lymph nodes spread so rapidly.

This connection to the lymphatic system is also interesting because the last time scientists discovered a new part of the body, it too was connected to the lymphatic system: a system of vessels called the "central nervous system lymphatic vessels," which drain lymphatic fluid from the brain to the surrounding lymph nodes.

They believe the interstitium compartments act as a shock absorber that protects organs from tearing as they squeeze and pump during their daily functions. Moreover, since collagen bundles in lab settings are shown to generate electrical current, they suspect the same thing is happening within the compartments as organs and muscles bend and move. Theise thinks this might account for some of the responses people have to alternative medical treatments like acupuncture and myofascial release, which involves applying sustained pressure to myofascial connective tissue to relieve pain.

WHY THE INTERSTITIUM REMAINED HIDDEN FOR SO LONG

Prior to this study, Theise says, the literature describing this interstitial space—often called "the third space" after the cardiovascular and lymphatic systems—has been vague. Part of the problem is that the structure of the interstitium can't be viewed when it's flat—and that's generally how it's been seen. When scientists prepare tissue to put onto slides for viewing under a microscope, they use chemicals to remove the fluids from it, and slice it thinly, causing the normally fluid-filled interstitial compartments to collapse.

Researchers had noticed "cracks" between collagen fibers in fixed slides, but, Theise says, they were always told these were just "artifacts of having torn the tissue."

However, in the fall of 2015, researchers from Mount Sinai Beth Israel Medical Center discovered the true shape of the interstitium by accident when testing out a new technology called probe-based confocal laser endomicroscopy, which offers a microscopic view of living tissue. In this procedure, a thin, camera-bearing probe called an endoscope is snaked down a patient's throat, where scientists can view the insides of organs with a laser that lights the tissues, and a sensor that analyzes the reflected light. There, while scoping a patient's bile ducts, the researchers, who are co-authors on the current paper, saw something they'd never seen before: the interconnected, fluid-filled compartments.

The discovery opens numerous avenues for research. Theise's team will most immediately use the research to look at a rare liver disease they now think may begin inside the interstitial compartments. Next, they'll be gathering all the bits and pieces of information they have on the interstitium for a comprehensive literature review, Theise says, "organ by organ, cell by cell, and disease by disease."

10 Smart Facts About Your Gut

Colorized scanning electron micrograph of E. coli, a common gut bacteria
Colorized scanning electron micrograph of E. coli, a common gut bacteria
National Institute of Allergy and Infectious Diseases, Flickr // CC BY 2.0

Gut feelings get all the press, but your gut may be more of a thinker than you know. Some scientists now consider it a second brain. While it won’t necessarily help you study for an exam or get a promotion, your gut can influence the chemistry of your mood, emotions, immune system, and long-term health. Research even suggests the gut can “learn” new tricks through conditioning. These powerful connections are part an emerging field of science called neurogastroenterology designed to study the gut-brain link. Here are 10 facts you may not know about your gut.

1. THE GUT DOESN'T NEED THE BRAIN'S INPUT. 

You might think of your gut as a rebel against authority. It doesn’t wait for your brain’s impulses to do the important work of digestion, because it doesn’t need to—it acts as its own “brain.” No other organ, not even the all-powerful heart, can pull that off.

2. THERE ARE MORE THAN 100 MILLION BRAIN CELLS IN YOUR GUT.

Your gut’s power to think for itself is no surprise; there are millions of neurons in its lengthy coils (9 meters of intestines, from esophagus to anus). That’s more neurons than are found in the spinal cord or peripheral nervous system.

3. YOUR GUT HAS ITS OWN NERVOUS SYSTEM.

The enteric nervous system—the controlling mechanism of digestion and elimination—is the overlord of your gut, and functions all on its own. Some scientists see it as part of the central nervous system, while others consider it its own entity. It likely evolved to give the gut the go-ahead when the “got to go” impulse strikes, without requiring the brain’s sign-off, particularly when you consider the helplessness of an infant with its brand-new brain.

4. THERE'S AN INFORMATION HIGHWAY FROM YOUR GUT TO YOUR BRAIN.

There’s one big visceral nerve embedded in your gut—the vagus nerve. Research has revealed that up to 90 percent of its fibers carry information from the gut to the brain, rather than the other way around. In other words, the brain interprets gut signals as emotions. So you really should trust your gut.

5. MOST OF YOUR SEROTONIN IS IN YOUR GUT.

Some 95 percent of your body’s serotonin, that marvelous mood molecule that antidepressant drugs like Prozac keep in your body, can be found in the gut. So, it’s no wonder that diet, medications, and antibiotics can wreak havoc on one’s mood.

6. A HEALTHY GUT MAY PROTECT YOUR BONES.

In a study of the serotonin-gut relationship, scientists discovered an unexpected link between the gut and the bones. Inhibiting the gut’s release of serotonin counteracted the bone-density reduction of osteoporosis in mice. This research is going into studies on new osteoporosis-fighting drugs.

7. RESEARCH SHOWS LINKS BETWEEN AUTISM AND HAVING FEWER STRAINS OF GUT BACTERIA. 

In as many as nine out of 10 cases, autistic people have common gut imbalances such as leaky gut syndrome, irritable bowel syndrome, and fewer strains of “good” bacteria. Research on mice is looking at possible treatments of some of the behavioral disorders of autism by balancing microbes in the guts, though many warn that such treatments can’t produce a “cure” for autism.

8. FOOD REALLY DOES AFFECT YOUR MOOD. 

Different foods, when introduced to the gut via feeding tubes, have been shown to change a person's moods without the person’s awareness of what they were "eating." Fat, for instance, increased feelings of happiness and pleasure (no surprise there) because appeared to trigger the release of dopamine—the brain’s natural opiate. Carbohydrate consumption stimulated the release of serotonin, the “feel good” neurotransmitter.

9. YOUR GUT IS YOUR BEST FRIEND IN COLD AND FLU SEASON.

Not only does your gut hold brain cells, it also houses the bulk of your immune cells—70 percent—in the form of gut associated lymphoid tissue, or GALT, which plays a huge part in killing and expelling pathogens. GALT and your gut microbiome—the trillions of bacteria that live, like an immense microbial universe, in your gut—work hard to help you get over what ails you. That’s all the more reason to be careful with the use of antibiotics, which wipe out the good bacteria along with the bad.

10. YOUR GUT CAN BECOME ADDICTED TO OPIATES.

Inside your gut are opiate receptors, which are also found in the brain. The gut is just as susceptible to addiction as the brain and may contribute to the intense difficulty some addicts have trying to kick the habit.

What Causes Hiccups?

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iStock/damircudic

The cause of hiccups depends on whom you ask. The ancient Greek physician Galen thought hiccups were violent emotions erupting from the body, while others thought they were a sign of liver inflammation. Today, evidence points to spasms in the diaphragm, the large muscle between the chest and abdomen that aids airflow during breathing. This involuntary contraction can be brought on by a number of things that might irritate the nerves that control the movement of the muscle. A full stomach, heavy boozing, rapid shifts in temperature either inside or outside of the stomach, and certain emotions like shock or excitement are all common culprits.

No matter the cause, the result is the same: The diaphragm spasms and causes us to take a quick breath. The sudden rush of air causes the epiglottis (the flap that protects the space between the vocal cords) to shut and interrupt the breath, which makes the familiar "hic" sound.

WHAT CURES THEM?

The best cure for hiccups also depends on the person you ask. Almost all cures are based on one of two principles: One type works its magic by overwhelming the vagus nerve with another sensation. The vagus nerve is a cranial nerve that innervates the stomach and conveys sensory information about the body's organs to the brain. When distracted by overwhelming information of another sort, it basically tells the brain that something more important has come up and the hiccuping should probably be stopped (vagus nerve stimulation is also used to control seizures in epileptics and treat drug-resistant cases of clinical depression). The other method for curing hiccups is to interfere with the breathing, increasing the amount of carbon dioxide in the blood, and causing the body to focus on getting rid of the of the CO2 and not making hiccups.

Swallowing a spoonful of sugar is probably the most commonly prescribed hiccup cure and falls into the first category. A teaspoon of sugar is usually enough to stimulate the vagus nerve and make the body forget all about the hiccups. Even ardent supporters of the sugar cure disagree if the sugar should be taken dry or washed down with water, though.

If this home remedy doesn't work, and your hiccups are both severe and persistent, you may need to bring out the big guns. For chronic cases like this, doctors sometimes use a cocktail of Reglan (a gastrointestinal stimulant) and Thorazine (an anti-psychotic with sedative properties) to quiet things down. In some cases that resist these drugs, Kemstro, an anti-spasmodic, is also used. Other doctors have used vagus nerve stimulators implanted in the upper chest of patients. The pacemaker-like devices send rhythmic bursts of electricity through the vagus nerve to the brain to keep the hiccup cycle in check.

Many people prefer home remedies to battle their hiccups, which may include holding your breath, gargling ice water, or breathing into a paper bag. While the same people will swear by the treatment they've been using all these years, there's no firm scientific consensus that any of them actually work. But if it helps you, isn't that all that matters?

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

An earlier version of this article appeared in 2012.

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