The mesentery is an anatomical structure that has recently garnered significant attention within the medical and scientific communities. For centuries, this tissue was largely considered a fragmented, secondary structure of the abdomen. Modern research, however, led to a dramatic re-evaluation of its form and function. This new understanding classifies the mesentery as a single, continuous organ, which has profound implications for abdominal surgery and disease.
Defining the Mesentery
The mesentery is a double fold of the peritoneum, the membrane lining the abdominal cavity, which attaches the small and large intestines to the posterior abdominal wall. For much of modern history, anatomical texts described the mesentery as several separate, disconnected structures. This fragmented view persisted despite earlier observations by Renaissance anatomists who depicted it as a continuous unit. The conventional model was based on descriptions suggesting parts of the mesentery disappeared or fused to the abdominal wall in adults.
A major paradigm shift occurred around 2012, when detailed microscopic examinations demonstrated the structure’s continuity. Researchers found the mesentery extends as one contiguous sheet from the duodenojejunal flexure to the mesorectum, spanning the entire gastrointestinal tract. This continuity led to its formal characterization as a single, fully connected structure, and by 2017, it was proposed for classification as a distinct organ. Recognizing it as a continuous organ corrects a long-standing anatomical error and provides a new framework, called the Mesenteric Model of Abdominal Anatomy.
Essential Functions of the Mesentery
Beyond its function as a tether, the mesentery serves several active physiological roles indispensable for digestive health. It acts as a conduit for the vast network of vessels and nerves that supply the intestines. The superior and inferior mesenteric arteries travel within the mesentery, providing oxygenated blood to the midgut and hindgut structures. This structure also contains the superior mesenteric nerve plexus, which transmits signals to regulate intestinal motility and secretion.
The mesentery provides the mechanical support necessary to secure the intestines to the back wall of the abdomen. This anchoring prevents the intestines from collapsing or twisting, a condition known as volvulus, while still allowing the necessary freedom of movement for digestion. It is also deeply integrated into the body’s defense system, performing immune surveillance.
It houses numerous lymph nodes positioned to filter the lymphatic fluid draining from the intestines. These lymph nodes contain immune cells that monitor the gut environment for pathogens. Visceral adipose tissue within the mesentery is metabolically active and helps modulate the body’s inflammatory response.
The Mesentery’s Role in Disease
The mesentery’s continuity and active functions mean it is intimately involved in the pathology of many abdominal conditions. In Inflammatory Bowel Disease (IBD), particularly Crohn’s disease, the mesenteric fat surrounding the affected area often thickens and wraps around the intestine, a phenomenon known as “creeping fat.” This visceral adipose tissue acts like an endocrine organ, secreting pro-inflammatory molecules that perpetuate intestinal inflammation.
The mesentery also functions as a pathway for the spread of abdominal cancers. Its rich network of blood vessels and lymphatics facilitates the metastasis of tumors, especially those originating in the colon or rectum. Metastatic cancer cells are detected in the mesentery of a significant percentage of colorectal cancer patients.
This clinical reality has driven the evolution of surgical techniques to treat the mesentery as a single, intact unit. Procedures such as Total Mesorectal Excision (TME) and Complete Mesocolic Excision (CME) involve removing the entire mesenteric package along with the diseased segment of the bowel. Excising the mesentery intact ensures the removal of all associated lymph nodes and potential microscopic tumor deposits, reducing the rate of local cancer recurrence.