For centuries, a structure within the human abdomen was largely overlooked and considered a set of disconnected parts. Scientific understanding has recently shifted, leading to the reclassification of the mesentery as a single, continuous organ. This change has opened a new area of medical science, prompting deeper investigation into its function within the digestive system. This revised status highlights its importance in health and disease, altering how surgeons and scientists approach the abdomen.
Anatomy of the Mesentery
The mesentery is a double fold of the peritoneum, the membrane lining the abdominal cavity. This sheet-like structure connects the intestines to the posterior abdominal wall. It extends from the upper small intestine down to the rectum. This continuous nature is a primary feature of its modern anatomical definition.
Visually, the mesentery resembles a fan, with its base attached to the back of the abdominal wall. From this attachment, it spreads out to envelop the loops of the small and large intestines. This structure contains loose connective tissue, fat, blood vessels, lymphatic vessels, and nerves held between its two peritoneal layers. This arrangement allows it to be both strong and flexible, providing support while permitting movement for digestion.
The mesentery is organized into regions named for the part of the intestine they support, such as the mesentery of the small intestine, the transverse mesocolon, and the sigmoid mesocolon. Despite these names, detailed observation has confirmed they are all parts of one contiguous structure.
Functions of the Mesentery
The primary role of the mesentery is to anchor the intestines, holding them in a specific position relative to the abdominal wall. This support prevents the intestines from collapsing into the pelvis when a person is standing or moving.
The mesentery serves as a conduit for blood vessels—both arteries and veins—that supply the intestines. The superior and inferior mesenteric arteries travel through it to deliver oxygen-rich blood, while the corresponding veins remove deoxygenated blood. This vascular network is fundamental for the metabolic activities of the gut.
Beyond blood supply, the mesentery is a pathway for nerves and lymphatic vessels. Nerves within it connect the gut to the central nervous system, playing a part in gut motility and sensation. The lymphatic system, including lymph nodes, is part of the body’s immune system and monitors the intestinal environment to initiate immune responses.
The mesentery is also involved in regulating inflammation. It plays a role in inflammatory conditions like Crohn’s disease. The tissue within the mesentery, including its fat deposits, is metabolically active and contributes to bodily functions beyond simple structural support.
Reclassification as an Organ
For more than a century, the medical view established by Sir Frederick Treves in 1885 was that the mesentery was a series of separate, fragmented structures. This perspective depicted different mesenteries for different parts of the intestine. This fragmented model was taught in medical schools for generations.
This long-held understanding was challenged by research from Dr. J. Calvin Coffey at the University of Limerick. Through detailed examination of patients undergoing colorectal surgery, his team demonstrated that the mesentery is a single, continuous structure. This discovery, published in 2016, provided the evidence to propose its reclassification as an organ.
The reclassification has significant implications for medicine. Viewing the mesentery as an integrated organ provides a new framework for understanding the abdomen and its anatomical relationships. It has already led to less invasive and more precise surgical techniques, particularly in colorectal surgery.
This new status has established “mesenteric science” as a specific field of study. Researchers are now exploring the mesentery’s role in a variety of diseases, including inflammatory bowel disease, diverticulosis, and colorectal cancer. Understanding how this organ functions opens potential new avenues for diagnosis and treatment.
Conditions Affecting the Mesentery
Several medical conditions can directly involve the mesentery. One is mesenteric ischemia, which occurs when blood flow to the intestines through the mesenteric arteries is restricted. This lack of oxygen can cause severe damage to the intestinal tissue.
Another condition is a volvulus, where a loop of intestine twists around its mesenteric attachment point. This twisting can obstruct the bowel and cut off its blood supply, leading to tissue death if not treated promptly. The structure of the mesentery, which provides a mobile anchor, is what makes a volvulus possible.
Inflammation can also affect the mesentery. Mesenteric adenitis is the inflammation of the lymph nodes within the mesentery. This condition is most common in children and can cause abdominal pain that mimics appendicitis. It is caused by a viral or bacterial infection.