Say hi to Mesentery, the ‘New’ organ in your body

The mesentery was considered a part of the digestive tract, but now two scientists say it’s actually the 79th organ in our bodies. It was once thought to be made up of separate structures, but it has been revealed in recent research to be one continuous organ. The organ is responsible for transporting blood and lymphatic fluid between the intestine and the rest of the body.

According to J. Calvin Coffey, Ph.D., F.R.C.S., professor of surgery at the Graduate Entry Medical School, University of Limerick, and University Hospitals Limerick, in Ireland, “We are now saying we have an organ in the body which hasn’t been acknowledged as such to date. This means that classic anatomic teaching, which spoke about multiple separate mesenteries, was incorrect, and that the mesentery associated with the small and large bowel were in actual fact one substantive structure,” Coffey said.

So, medical students who memorized the number 78 as the number of organs in the human body should plan on a little revisionist brainwork to remember the number 79.

The discovery is only the first step, Coffey said. While the mesentery’s structure is known, its function is not.

Further study could lead to better understanding and treatment of abdominal and digestive disease. “Now we have established anatomy and the structure, the next step is the function,” Coffey told ScienceAlert.

“If you understand the function you can identify abnormal function, and then you have disease. Put them all together and you have the field of mesenteric science … the basis for a whole new area of science,” he said. “This is relevant universally as it affects all of us.”

Thanks to the new research, as of last year, medical students started being taught that the mesentery is a distinct organ. The world's best-known series of medical textbooks, Gray's Anatomy, has even been updated to include the new definition.

So what is the mesentery? It's a double fold of peritoneum - the lining of the abdominal cavity - that attaches our intestine to the wall of our abdomen, and keeps everything locked in place.

One of the earliest descriptions of the mesentery was made by Leonardo da Vinci, and for centuries it was generally ignored as a type of insignificant attachment. Over the past century, doctors who studied the mesentery assumed it was a fragmented structure made of separate sections, which made it pretty unimportant.

But in 2012, Coffey and his colleagues showed through detailed microscopic examinations that the mesentery is actually a continuous structure.

Over the past four years, they've gathered further evidence that the mesentery should actually be classified as its own distinct organ, and the latest paper makes it official.