The mesentery is a structure within the abdomen that supports and organizes the digestive system. It is a continuous fold of tissue that connects the intestines to the back wall of the belly, ensuring they remain in their proper place. Recognizing its distinct nature has opened up new areas of medical study and changed how surgeons approach abdominal disease.
Anatomy and Physical Structure
The mesentery is formed by a continuous double layer of the peritoneum, the membrane lining the abdominal cavity. This tissue structure is made up primarily of connective tissue and fat, and it acts as a suspension system for the intestines. The mesentery attaches the small intestine and parts of the large intestine to the posterior abdominal wall.
It is often described as being fan-shaped, allowing the long segments of the intestine to be stored within the abdominal space. The structure begins at a narrow point, known as the root, near a major abdominal artery, and then spreads out across the abdominal cavity. This unique shape provides flexibility for the intestines to move during digestion while simultaneously preventing them from collapsing or twisting upon themselves.
The mesentery is a single, continuous structure, though different sections are named based on the part of the intestine they attach to. The section connected to the small intestine’s jejunum and ileum is referred to as the mesentery proper, while the part connecting the colon is called the mesocolon.
Reclassification as a Distinct Organ
For centuries, the mesentery was viewed as a collection of separate, disconnected structures. This historical perspective meant the mesentery did not receive the dedicated scientific focus given to other organs.
A turning point came with modern research using detailed microscopic techniques to re-examine the structure. Beginning around 2012, a research team formally confirmed that the mesentery is a single, continuous structure spanning from the duodenum to the rectum. This anatomical clarity provided the necessary evidence to support its designation as a distinct organ.
This reclassification encourages scientists to approach the mesentery as a unified system with its own pathology and physiology, similar to the approach taken with the liver or heart. The updated understanding led to a change in major medical textbooks, signaling a new field of study called “mesenteric science.”
Physiological Functions
The mesentery serves as the primary conduit for the intestinal blood supply. It contains the superior and inferior mesenteric arteries and veins, which branch off the abdominal aorta. These vessels deliver oxygenated blood to the intestines and carry nutrient-rich, deoxygenated blood away. Without the mesentery, the extensive network of blood vessels required to sustain the long segments of the gut would be disorganized.
The mesentery is a significant hub for the immune system. It is densely packed with lymph nodes and lymphatic channels that monitor the contents of the gut. This network acts as a surveillance system, trapping germs and sampling bacteria from the intestine to initiate an immune response when necessary. This regulation of inflammation affects the entire digestive tract.
The mesentery provides structural support, anchoring the intestines firmly to the abdominal wall to prevent torsion, or twisting, which can cut off blood flow. Furthermore, the mesentery is composed of fat cells, known as mesenteric adipose tissue. These cells contribute to metabolic health and can produce signaling molecules, including C-reactive protein, which helps regulate inflammation and blood sugar.
Clinical Relevance in Modern Medicine
The recognition of the mesentery as a unified organ has implications for surgical procedures. Surgeons now utilize standardized approaches like Total Mesenteric Excision (TME) for rectal cancer and Complete Mesocolic Excision (CME) for colon cancer. These techniques involve excising the cancerous segment of the bowel along with its entire associated mesentery. This is believed to improve patient outcomes by ensuring all cancer-containing lymph nodes are removed along the defined, continuous fascial plane.
Abnormalities in the mesentery, such as the thickening and stiffening of its tissue, are characteristic features of Crohn’s disease. Research suggests that including a wide excision of the mesentery during surgery for Crohn’s disease may reduce the rate of recurrence for patients. This indicates that the mesentery itself contributes to the disease process.
The mesentery is a promising target for future drug delivery and therapeutic research. Understanding the crosstalk between the various components within the mesentery, such as its fat cells and nerves, may lead to new treatments for complex conditions like irritable bowel syndrome and metabolic disorders. This new perspective positions the mesentery as a central player in abdominal health and disease.