The mesentery was once thought to be part of the digestive tract, but two scientists say it’s actually the 79th organ in our bodies.
The announcement that the human body has a new organ may help to reestablish balance in a universe that’s been tilted off its axis ever since Pluto was downgraded to a dwarf planet.
The “new” organ is called the mesentery, and everybody’s digestive tract has one.
The mesentery 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.”
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Coffey, and his colleague Peter O’Leary, Ph.D., first discovered that the mesentery was an organ.
In an email, Coffey explained his discovery to Healthline this way, “I am primarily a surgeon who operates on the large bowel and rectum. I noticed that the technique we use on the left colon has the same anatomic basis as the techniques we use on the right.
“When I looked at this closer I noticed the reason for this was that the right and left colon have an attached mesentery. (In every patient. That is, universally.)”
His curiosity piqued, Coffey did a study “examining surgical findings closer and noticed that — yes indeed — both right and left regions of the colon do have a distinct and substantive mesentery.”
In addition, these regions of the mesentery were continuous with the regions of the mesentery associated with the small intestine, transverse colon, sigmoid colon, and rectum, he said.
In effect, it is all one continuous structure.
“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.
He pointed out that 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.”
As a trained surgeon, Coffey is aware that, “According to classic anatomic teaching, the right and left colon do not have an attached mesentery and, if a mesentery were present, then this should be considered anomalous.”
He went on to tell Healthline, “Some texts suggested that the right and left colon did have a vestigial or rudimentary mesentery, attached immediately behind them. So, what we found surgically was very different to what we were taught anatomically.”
One sure sign of its change in status is that the mesentery has been accepted as an organ in “Gray’s Anatomy,” the best-known series of medical textbooks in the world.
Although no one in the field seemed to know who the final authority is for saying “Yea” or “Nay” to organ status, the evidence for this organ’s reclassification is now published in
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All this recognition has been centuries in coming.
Leonardo da Vinci described the mesentery in the 15th century, but not much attention was paid to it. It seemed to be a kind of insignificant attachment.
So now that we have classified this new organ, what good does it do us?
Coffey said the mesentery now becomes a valuable structure to study.
“There are a lot of diseases that we are stalled on, and we need to refresh our approach to these diseases,” Coffey told Smithsonian.com.
“Now that we’ve clarified its structure, we can systematically examine it. We’re at a very exciting place right now,” he said.
However, it’s not likely that the discovery of the mesentery will earn any new respect for its neighbor, the vestigial appendix.
“Since we now know the anatomy of the mesentery, we also have a better understanding of the mesentery associated with the appendix [mesoappendix],” Coffey said. “The mesoappendix extends from the undersurface of the mesentery in the region where the small intestine continues as the right colon.”
Pluto, eat your dwarf planet heart out.