The discovery of the body’s 79th organ prompted an update to the famous Gray’s Anatomy textbook, which is used by medical students around the world. 
Named the mesentery, the organ was previously thought to consist of fragmented and disparate structures. Researchers found, however, that it is one continuous organ and outlined evidence to classify it as such in a review published in The Lancet Gastroenterology & Hepatology.
“In the paper, which has been peer reviewed and assessed, we are now saying we have an organ in the body which hasn’t been acknowledged as such to date,” J. Calvin Coffey, a researcher from the University Hospital Limerick in Ireland, who first made the discovery, said in a release.
The mesentery is a double fold of the peritoneum, which is the lining of the abdominal cavity. It connects the intestine to the abdomen.
Among its functions, it carries blood and lymphatic fluid between the intestine and the rest of the body. It also maintains the position of the intestine so that it's connected with the abdominal wall without being in direct contact.
That connection is key.
"Without a mesentery to keep the intestine connected, the intestine would have to attach directly to the body wall," Coffey said. "It is unlikely that it would be able to contract and relax along its entire length if it were directly in contact. It maintains the intestine in a particular conformation, 'hitched up,' so that when you stand up or walk about, it doesn't collapse into the pelvis and not function."
Although researchers know that the mesentery plays an important role in the intestinal, vascular, endocrine, cardiovascular and immunological systems, more research is needed to determine the extent of those roles.
But they do have evidence that the mesentery takes environmental signals from the intestine and orchestrates the body's response, Coffey said. One example is how bacteria are sampled in the lymph glands in the mesentery. In response, the glands then coordinate immune responses.