The Interstitium Is Important, But Don’t Call It An Organ (Yet)

By Nathaniel Scharping | March 28, 2018 3:45 pm

Some organs, maybe. (Credit: Komsan Loonprom/Shutterstock)

Humans might have a new organ, and the press is all over it—again.

In brief: It’s called the interstitium, or a layer of fluid-filled pockets hemmed in by collagen and it can be found all over our bodies, from skin to muscles to our digestive system. The interstitium likely acts as a kind of shock absorber for the rest of our interior bits and bobs and the workings of the fluid itself could help explain everything from tumor growth to how cells move within our bodies. The authors stop short of saying “new organ,” but the word is certainly on everyone’s lips.

Is it just me, or are you feeling a bit of deja vu?

Well, maybe it’s just me, but that’s because I’ve been in this situation before. You see, just over a year ago, researchers announced that they’d discovered a different “new” organ — the mesentery. That particular collection of bodily tissue is a fan-shaped fold that helps hold our guts in place. It had been known about for centuries, but only recently discovered to be large and important enough to justify calling it an organ. It was to be the body’s 79th, but that number is entirely arbitrary.

As we discovered here at Discover, the definition of an organ is hardly settled (and we’re aware of what a church organ is, thankyouverymuch). As became apparent during the whole mesentery craze, there’s no real definition for what an organ actually is. And the human body doesn’t have 79 organs, or 80 organs, or 1,000 organs, because that number can change drastically depending on the definition. And you can bet scientists debate what an organ actually is.

“It’s a silly number,” said Paul Neumann, a professor of medicine at Dalhousie University in Canada and member of the Federative International Programme for Anatomical Terminology, in a Discover article from last year. “If a bone is an organ, there’s 206 organs right there. No two anatomists will agree on a list of organs in the body”

Calling the interstitium a new organ, then, is a bit of a stretch. It’s there, it’s certainly important, but we need a better idea of what an organ is before we can start labeling things as such.

There is a definition of sorts, but it’s got more wiggle room than your large intestine. An organ is composed of two or more tissues, is self-contained and performs a specific function, according to most definitions you get by Googling “what is an organ?” But there’s no governing body that explicitly determines what an organ is, and there’s no official definition. Things like skin, nipples, eyeballs, mesenteries and more have crossed into organ-dom and back throughout history as anatomists debated the definition.

It may seem like mere semantics, but nailing a definition for an organ could actually turn out to be quite important. As we wrote last year, medical data is increasingly being stored in the cloud and analyzed by artificial intelligence algorithms that help researchers make new discoveries or diagnose maladies. The artificial intelligence-assisted algorithms that pore through all that data need things to be defined both clearly and consistently if they’re going to do their job correctly—an organ in one place should be an organ in another. Inconsistencies are going to throw a wrench into search results.

This doesn’t change the fact that most every part of our body is important, though. Regardless of whether we call the liver an organ or not, we still need it to function. Ditto for the mesentery and the latest assemblage of cells to bear the dubious honorific.

An illustration of the interstitium, which may or may not be an organ. (Credit: Jill Gregory/Mount Sinai Health System)

An illustration of the interstitium, which may or may not be an organ. (Credit: Jill Gregory/Mount Sinai Health System)

The interstitium could actually turn out to be quite important. Researchers hadn’t noticed it before because the way they obtained tissue samples seems to have destroyed a crucial portion of the tissue. The fluid-filled pockets would leak and collapse when removed and preserved, obscuring all evidence of an interstitium. But using a new technique involving an endoscopic camera, lasers and fluorescent dye, two researchers found an odd pattern in the bile ducts of patients they were examining. When they removed and flash froze the tissue, they found a network of fluid-filled pockets that they had never seen before. And upon further study, the same structures showed up throughout the body, they found in research published in Scientific Reports.

In addition to cushioning organs inside our bodies, the fluid sacs could help transport white blood cells, molecules used for signaling and more. The authors even suggest that samples of the fluid could be used to diagnose diseases. Finding something entirely new in the human body is a little bit amazing, especially in an age where we assume we know ourselves completely, and it could help to clear up some as-yet-unresolved questions in medicine.

Whether you call the interstitium an organ, or refuse to bestow that definition on this hunk of tissue, you aren’t wrong. Gray’s Anatomy, a medical Bible if there ever was one, did after all recognize the mesentery as an organ last year. And really, that’s fine. It won’t change how we study the interstitium, it won’t much change how we talk about it, and it certainly won’t cause it to function any differently.

CATEGORIZED UNDER: Health & Medicine, top posts
  • Uncle Al

    I’ll say it, quietly, “POSSIBLE CANCER CURE IS HINTED BY NEW ORGAN STUDY,” a concept originally found in jellyfish.

    • Nikunj Dhandhukiya

      Yes, it is possible… For cancer cure.. When thing is born.. It is definitely to Death. Cancer is one of them &it is rule of god. No single living body is stay……. All have one day destroyed.

      • StanChaz

        If we are are – in a very real sense – star dust my friend, can we ever really die and be so cruelly destroyed?

        Is that all there is to being human, to being conscious, to being alive, and to knowing that we’re alive and aware and part of it all?

        Or are we gods and animals and swirling dust & dirt, a continuity in the flow and dance of the universe, over and over, forever and ever, …amen?

        My religion is one of questions, not answers; a journey, not a place; a seeking not a solution; a wonder, awe and openness to life and all its potentials, here and now – not the abyss of black-hole whirlpools of death, despair and destruction;

        Lift up thine eyes instead. For as Leonard Cohen once sang: “We are so small between the stars, and yet so large against the sky. And lost among the subway crowds I try to catch your eye…

  • whosonfirst

    Maybe they need a term, or two or more, between tissue and organ. And if each bone is an organ then how many of these fluid pockets would be an organ which would move the count into the millions. I would suggest restricting “organ” to be “there is only one”. If there are more than one example of something then a word derived from “template” or similar word. In the programming sphere the single instance is called a “singleton” the template is a “class” and you have customization as “instances” or instantiations.

    • Danny Gentile

      That means the kidneys and lungs wouldn’t be organs and that’s just silly. It seems like the interstitium is considered one big one, like skin, though, not as counting individual pockets or whatever.

  • GeoFox190

    Maybe it should be demoted to a “dwarf organ”

    • Ray Franklin

      Or to the “red-headed step-child organ”

  • StanChaz

    Will wonders never cease ….belatedly?
    A brand new organ discovered — right before our hyperopic scientific eyes! In fact, quite literally right under our upturned and oh-so-smug noses.

    I wonder when (and if) these “experts” will discover the true meanings and implications of that most mysterious, majestic and fundamental of human “organs”: human consciousness, the spark of life, the crown of creation, the universe born into its own awareness, finally, after so many lonely eons of silence; A human consciousness which all-too-often is simplistically dismissed as some easily discarded curdle that floats on top of a mechanistically derived cream. Nothing special here folks. Move on. Nothing to see. Next please.

    The reality is that there are many more things than are dreamt of in your fledgling, immature, and woefully incomplete sciences….

  • Hussain Shaikh

    Yes sir u r right.

    There is no fix scientific definition for organ.
    If interstitium is an organ then nail,teeth should be an organ.

    Both of these perform specific function.

    • applecreeker

      And Pluto is not a “planet”!!!

    • Confused

      teeth are organs!!!!

  • Darmi

    Heard a rumor that the interstitium may play a role in blood circulation, specifically through the venous system. What do you think?

  • Ram

    Underscores the need to approach the human body and all its aspects with humility. As doctors, we sometimes make sweeping statements about a person’s health and prognosis. I am sure this is just one of many new revelations that will unfold in the years to come.

  • S. Fox

    The thing I like.about this, it points out the arrogance and pomposity of man. Whoops! You mean there is something of the human anatomy we don’t know? Horrors!

    When medical science is shown not only to not know the answer but, they haven’t got a clue about the question, I’m a happy camper. This seems to be one of those times.


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