The omentum majus is the name given to a duplication of the peritoneum that is rich in fatty tissue. The structure plays an important role in immune defense in the abdominal region.
What is omentum majus?
The omentum majus is also known as the great mesh, intestinal mesh, abdominal mesh, or omentum gastrolicum. It refers to a structure that is covered by connective tissue and fat. It hangs down like an apron from the large curvature of the stomach as well as the portion of the colon that takes a transverse course (transverse colon). In this process, the greater omentum usually completely covers the loops of the small intestine. One of the tasks of the greater omentum is the immune defense of the abdominal cavity. Thus, it is also considered the “policeman of the abdomen”. Furthermore, it is important for storing fat and has a part in regulating the fluid balance in the peritoneal cavity.
Anatomy and structure
Similar to an apron, the omentum majus hangs down from the curvatura major (large curvature) of the stomach as well as the transverse colon. The ventral aspect of the abdominal organs is covered by it up to approximately the umbilical cavity. This is especially true of the small intestine (intestinum denue). On the left side of the body, it joins the gastrolienal ligament. The large mesh is traversed by various lymphatic vessels. It also has a good blood supply. The development of the greater omentum in the human body dates back to the third embryonic month. During this process, the dorsal mesentery develops fusing fissures. Through them the recessus pneumato-entericus dexter is formed. This initially provides a connection between the abdominal cavity and the chest. Its closure is ensured on the upper side by the diaphragm. The rotation of the stomach and the movement of the dorsal mesentery cause the formation of the omental bursa on the right side. This pouch, which is open on the right side, finally comes to rest behind the stomach. It functions as a displacement layer of the stomach and ensures its undisturbed mobility. Once the physical development of the human is complete, there is a large peritoneal niche in the peritoneal cavity. On the anterior side, the omentum majus is bounded by the omentum minus, the gastrocolic ligament and the stomach. On the posterior side, the peritoneum parietale provides the delineation of the structure. On the upper side, there are outpouchings in the form of the superior recessus. This runs between the esophagus and the inferior vena cava under the liver. In the lower direction, the inferior recess is located between the transverse colon and the stomach. There is a connection to the free abdominal cavity through the vestibulum bursae (vestibule of the pouch) as well as the foram epiplocicum. The omentum majus is divided into three structures. These are the ligamentum gastrolicum (gastrocolic ligament), the ligamentum gastrosplenicum as well as the ligamentum gastophrenicum. The gastrolic ligament extends between the greater curvature and transverse colon, while the gastrosplenic ligament extends between the greater curvature and splenic hilum. The course of the ligamentum gastrophrenicum extends from the gastric fundus toward the diaphragm.
Function and Tasks
Three functions are performed by the omentum majus. For example, the abdominal network plays an important role in immune defense because it has a large number of leukocytes and macrophages. In the event of inflammation, these lay down on the affected areas and, by sealing them, cause protection against dangerous peritonitis, which occurs due to a breakthrough of pus and intestinal contents. The intestinal mesh is also important for regulating the fluid balance within the peritoneal cavity. Thus, with the help of its extensive surface area, it ensures the balance of the fluid. Furthermore, the omentum majus participates in the absorption and release of peritoneal fluid in the peritoneal cavity. In addition, the abdominal mesh acts as a significant store of fat. In people who are prone to obesity, it can often be expanded to form a fat plate that has a thickness of several centimeters.
Diseases
The greater omentum can be affected by various diseases. Normally, the well-moving fat apron is able to tape off and cover inflammation. In doing so, it also glues the peritoneum together. However, this results in the formation of scars and adhesions. In medicine, these are called adhesions.In most cases, these adhesions are caused by surgical procedures within the abdominal cavity. Although surgery uses different substances and drugs to prevent the formation of adhesions, this is not always successful. However, adhesions are less likely to show up during minimally invasive surgery. The most common causes of adhesions to the abdominal mesh include gynecologic surgery, surgical removal of the appendix, and perforation of the stomach or intestines. In severe cases, adhesions form cords that extend through the abdominal cavity and resemble a cord. The cords pose a risk of entrapment of the bowel, which in turn results in bowel obstruction. The entrapment of the intestinal loops becomes noticeable through severe pain in the abdominal region. Furthermore, cramps as well as stool irregularities, diarrhea and constipation are possible. As a rule, surgery must be performed for treatment. It is not uncommon for the omentum majus to enter hernias in the abdominal wall region. The most common hernias of the abdominal cavity include incisional hernias, inguinal hernias as well as umbilical hernias. There is a risk of entrapment of the intestinal network in a hernia gap and circulatory disturbances. During surgery, the surgeon often has to remove parts of the greater omentum in addition to the inflamed organ.
