Mesentery is the general term often used to describe the double layer of peritoneum that supports the internal organs and suspends them from the abdominal and pelvic cavities. More specifically, it refers to the peritoneum associated with the ileum and jejunum of the small intestine. When referring specifically to the membrane supporting the small intestine, it is often referred to as the mesentery proper, to avoid confusion. The mesentery proper is anchored to the posterior abdominal wall along an area about 6 inches (about 15 cm) long, directly anterior to the vertebral column. Fan-shaped, the mesentery is more than 15 feet (about 6 m) in length at the point where it encloses the intestine itself.
Generally speaking, the peritoneum is comprised of two layers of serous membrane with a small amount of serous fluid between the layers. Together, the membrane and the fluid serve to reduce friction between the internal organs and allow smooth, easy motion of the body. Peritoneum exists throughout the thoracic, abdominal, and pelvic regions, but is only correctly termed the mesentery when associated with the intestines. The suffix -enteries is a diminutive of the Greek word enteron, meaning gut or entrails, and thus refers specifically to the intestines. Similarly, the mesogastrium refers to the peritoneum associated with the stomach, the mesometrium to the peritoneum of the uterus, and so on.
In addition to providing physical support, the mesentery carries the nerves, blood vessels, and lymph vessels that service the intestine. These vessels run between the membrane layers along with the serous fluid. Blood vessels typically supply oxygen to the intestines and carry nutrients from the digestive system to the rest of the body. Nerves relay messages to and from the central nervous system. A row of lymph nodes sits at the base of the mesentery and along with the lymph vessels, typically provide immune support for the intestines.
If blood supply through the mesentery is restricted, usually due to an underlying disorder of the blood vessels, a mesenteric infarction can occur. Acute mesenteric infarction normally presents with no symptoms until well advanced, at which time the condition is characterized by severe pain coupled with few other physical symptoms. Although acute mesenteric infarction accounts for only 0.1 percent of hospital admissions, mortality has been shown to be as high as 71 percent. With diagnosis and treatment within 10-12 hours of onset of symptoms, this number usually falls to about 55 percent.