Last fall, scientists announced the discovery of a new organ: the mesentery. Of course, the mesentery wasn’t completely unknown. The news is that it plays a much bigger role in health than scientists originally thought.
Most people think of paintings when they hear the name DaVinci, but Leonardo DaVinci was the first person to observe the body in great detail, preserved in a series of intricate drawings. His early works examining the inside of the abdomen did label the mesentery. He drew it as a single, continuous organ. In 1878, a guy named Carl Toldt reiterated this view of the mesentery as one structure. Mr. Toldt was ahead of his time.
Gray’s Anatomy, the definitive text on anatomy, first published in 1858 had described the mesentery as broken into pieces. This view was supported by Sir Frederick Treves, who believed in 1885 that the mesentery was in pieces. That was the final word on the mesentery until recently, when Dr. J. Calvin Coffey, chair of surgery at the University of Limerick rediscovered the continuity of the mesentery.
What is the mesentery?
The intestines are a long tube that are coiled in the abdomen. There are organized parts to the intestine, and food moves along them in one direction. From the stomach, food heads to the small intestines which are, in order: the duodenum, the jejunum, then the ileum. At the end of the ileum, the food moves on to the large intestine. The cecum is the beginning of the ascending colon, on the right side of the body. From there, food, now more stool than food, heads across the transverse colon, crosses to the left and moves downward through the descending colon on the left side of the body, into the sigmoid colon, rectum and exits through the anus.
Standing back and looking at that whole set of structures, the intestines look a bit like a floppy garden hose. Without some kind of support, the intestines would collapse into a heap in the pelvis every time anyone stood up. The ascending colon would not stay on the right and the descending colon wouldn’t stay on the left. One could only imagine the tangle the small intestines would be in.
The mesentery is a beautiful, complex way to anchor the intestines in place. The mesentery attaches to the peritoneum, which lines the abdomen and the organs. It has always been known that the mesentery supports the transverse colon along the top of the abdomen, the long, winding small intestines, and the sigmoid colon below it.
What is new is the realization that this organ is one, continuous organ. It does also support the ascending and descending colons along the sides of the abdomen, even though they stay pretty firmly in place and generally hang further back in the abdomen. It actually connects every single part of the intestinal tract, from the duodenum or possibly as high as the esophagus, to the rectum.
Why does this matter?
The mesentery isn’t just a suspension system. It is made up of blood vessels, lymph tissue, connective tissue and nerves. It helps the intestines move and twist. It is the point of contact between the intestines and the body wall. Recognizing that this point of contact goes all the way from the top of the digestive tract to the bottom, helps scientist and doctors understand disease.
The mesentery is important to so many different systems, it is hard to know how to classify it. While the intestines are clearly the digestive system, and the heart is the main organ of the cardiovascular system, the mesentery doesn’t have just one speciality. It is part of the cardiovascular system because it supplies blood to much of the digestive tract. It is part of the endocrine system because it is loaded with lymph tissue that responds to infections. It is clearly an important support and protector of the digestive tract.
Because it serves as a point of communication between all of these systems, the mesentery may finally unlock some of the most difficult questions in medicine. The new understanding that this is one organ that connects the very top of the GI tract with points much further along the gut may explain connections between esophageal problems and trouble in the lower intestines.
Inflammatory diseases such as Crohn’s Disease, which is considered an intestinal disorder affects other body systems as well. For example, arthritis and vision changes are common for people who have Crohn’s. The new research suggests that Crohn’s may actually begin in the mesentery, and then affect the intestines and other body systems. Can the mesentery’s rich supply of connective tissue help explain why or how inflammation travels to other tissue?
Surgeons are already revising how they approach abdominal procedures based on the realization that this is in fact one structure that should be kept intact. Imagining of the abdomen will now look at the whole mesentery when diagnosing conditions. The mesentery is the largest contributor to fat in the organs. This has a big impact on metabolic diseases such as diabetes, obesity and metabolic syndrome. Maybe changes in the mesentery are the cause of these diseases, not the result of them. This could be a huge breakthrough in understating and treating these difficult conditions.
The next steps for scientists will be to learn more about the cells of the mesentery. The mesentery is a complex organ and an important center of communication for the body. The more is understood about exactly how it functions at the cellular level, the more accurately medications can be developed to influence it, and the better we can understand how to support its function.
 The mesentery: structure, function, and role in disease. Coffey, J Calvin et al. The Lancet Gastroenterology & Hepatology , Volume 1 , Issue 3 , 238 – 247