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Say hello to your body's newest organ

Over a century ago, when scientists were classifying the body’s organs, one was short shrifted, according to researchers who say part of the digestive system deserves to be upgraded to organ status.

In a new medical journal report, scientists say the mesentery – connective tissue that winds around our digestive organs, holding them in place – isn’t a fragmented structure as once thought, but actually one contiguous structure.

“The anatomic description that had been laid down over 100 years of anatomy was incorrect. This organ is far from fragmented and complex,” said study author J. Calvin Coffey, from the University of Limerick, Ireland, in a press statement. “It is simply one continuous structure,” winding from the small intestine down to the rectum.

Medically speaking, an organ is self-contained and has a very specific vital job – think brain, kidneys and heart. Many, but not all, organs have a distinct functional unit, the study authors wrote in the Lancet Gastroenterology & Hepatology journal.

But there are still many questions about how the mesentery functions. “The functional unit of the mesentery is unknown, and whether a distinctive cell type is primarily responsible for its functionality should be investigated,” they said.

mesentery.jpg

A digital representation of the small and large intestines and mesentery.

The Lancet Gastroenterology & Hepatology Coffey, JC et al. 2016 The mesentery: structure, function, and role in disease.

Dr. Kevin Campbell, assistant professor of medicine at the University of North Carolina, told CBS News that the mesentery has been hiding in plain sight for centuries. In fact, artist and inventor Leonardo da Vinci’s (1452 – 1519) drawings suggest the structure’s existence was known even then. 

The new findings, though, may help researchers consider it in a fresh way that could help them better understand abdominal and digestive diseases.

“We’ve known this has been part of our bodies. We just don’t fully understand what role it plays. In the past, we’ve known that the mesentery was there basically just to hold all the organs in place inside our abdomen. And now we think that it may be one contiguous organ that actually may play a role in disease,” Campbell said.

Campbell said that when he studied anatomy in medical school in the nineties, he was taught that the mesentery was a set of fragmented tissues that held the belly’s organs in place.

“This is the first we’re hearing that it could be one contiguous organ. The researchers from Ireland looked at it under a microscope and really feel like it is one contiguous organ,” said Campbell.

That leads to the next big question: What exactly does it do beyond holding things in place?

mesentery-researcher.png

Mesentery researcher J. Calvin Coffey, professor of surgery at the University of Limerick, Ireland, Graduate Entry Medical School.

Alan Place, courtesy of the University of Limerick, Ireland

“Now we can design studies and we can do things that better determine what its function is, what its role in digestion is,” Campbell added.

For instance, right now, cancer surgeons often remove portions of the mesentery.

“Maybe that’s not the right thing to do. There are a lot of questions that this brings about and we still have more questions than answers,” Campbell said.

For now, the mesentery’s reputation is on the upswing. Last year, medical students started being taught that the it is an organ unto itself, and one of medicine’s best known textbooks, Gray’s Anatomy, now describes the mesentery as an organ.

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    Mary Brophy Marcus covers health and wellness for CBSNews.com