Greater omentum
Encyclopedia
The greater omentum is a large fold of parietal peritoneum
that hangs down from the stomach. It extends from the greater curvature of the stomach
, passing in front of the small intestines and reflects on itself to ascend to the transverse colon
before reaching to the posterior abdominal wall. The common anatomical term "epiploic" derives from "epiploon" from the Greek "epipleein" meaning to float or sail on, since the greater omentum appears to float on the surface of the intestines.
, folded on itself so that it is made up of four layers.
The two layers which descend from the greater curvature of the stomach and commencement of the duodenum
pass in front of the small intestine
s, sometimes as low down as the pelvis
; they then turn upon themselves, and ascend again as far as the transverse colon
, where they separate and enclose that part of the intestine.
These individual layers may be easily demonstrated in the young subject, but in the adult they are more or less inseparably blended.
The left border of the greater omentum is continuous with the gastrolienal ligament; its right border extends as far as the commencement of the duodenum
.
The greater omentum is usually thin, presents a cribriform
appearance, and always contains some adipose tissue
, which in obese people accumulates in considerable quantity.
The splenorenal ligament
(from the left kidney
to the spleen
) is occasionally considered part of the greater omentum.
provide the sole blood supply to the greater omentum. Both are branches of branches off of the celiac trunk. The right gastroepiploic is a branch of the gastroduodenal artery
, which is a branch of the common hepatic artery
, which is a branch of the celiac trunk. The left gastroepiploic artery is the largest branch of the splenic artery
, which is a branch of the celiac trunk. The right and left gastroepiploic vessels anastomose within the two layers of the anterior greater omentum along the greater curvature of the stomach.
that connects the stomach
to the posterior abdominal wall. During stomach development, the stomach undergoes its first 90° rotation along the axis of the embryo, so that posterior structures are moved to the left and structures anterior to the stomach are shifted to the right. As a result, the dorsal mesentery folds over on itself, forming a pouch with its blind end on the left side of the embryo. A second approximately 90° rotation of the stomach, this time in the frontal plane, moves structures inferior if they were originally to the left of the stomach, and superior if they were originally to the stomach's right. Consequently, the blind-ended sac (also called the lesser sac
) formed by the dorsal mesentery is brought inferiorly, where it assumes its final position as the greater omentum. It grows to the point that it covers the majority of the small and large intestine.
and advanced or aggressive endometrial cancer
as well as intestinal cancer. The procedure is generally done as an add-on when the primary lesion is removed.
Peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
that hangs down from the stomach. It extends from the greater curvature of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, passing in front of the small intestines and reflects on itself to ascend to the transverse colon
Transverse colon
The transverse colon, the longest and most movable part of the colon, passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath...
before reaching to the posterior abdominal wall. The common anatomical term "epiploic" derives from "epiploon" from the Greek "epipleein" meaning to float or sail on, since the greater omentum appears to float on the surface of the intestines.
Functions
The functions of the greater omentum are:- Fat deposition, having varying amounts of adipose tissueAdipose tissueIn histology, adipose tissue or body fat or fat depot or just fat is loose connective tissue composed of adipocytes. It is technically composed of roughly only 80% fat; fat in its solitary state exists in the liver and muscles. Adipose tissue is derived from lipoblasts...
- Immune contribution, having milky spots of macrophageMacrophageMacrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
collections - Infection and wound isolation; It may also physically limit the spread of intraperitoneal infections. The greater omentum can often be found wrapped around areas of infection and trauma.
Structure
The greater omentum is the largest peritoneal fold. It consists of a double sheet of peritoneumPeritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
, folded on itself so that it is made up of four layers.
The two layers which descend from the greater curvature of the stomach and commencement of the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
pass in front of the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
s, sometimes as low down as the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
; they then turn upon themselves, and ascend again as far as the transverse colon
Transverse colon
The transverse colon, the longest and most movable part of the colon, passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath...
, where they separate and enclose that part of the intestine.
These individual layers may be easily demonstrated in the young subject, but in the adult they are more or less inseparably blended.
The left border of the greater omentum is continuous with the gastrolienal ligament; its right border extends as far as the commencement of the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
.
The greater omentum is usually thin, presents a cribriform
Cribriform
Cribriform can refer to:* Cribriform plate* Fascia cribrosa* Cribriform mesenchyme...
appearance, and always contains some adipose tissue
Adipose tissue
In histology, adipose tissue or body fat or fat depot or just fat is loose connective tissue composed of adipocytes. It is technically composed of roughly only 80% fat; fat in its solitary state exists in the liver and muscles. Adipose tissue is derived from lipoblasts...
, which in obese people accumulates in considerable quantity.
Subdivisions
The greater omentum is often defined to encompass a variety of structures. Most sources include the following three:- Gastrocolic ligamentGastrocolic ligamentThe gastrocolic ligament is a portion of the greater omentum that stretches from the greater curvature of the stomach to the transverse colon. It forms part of the anterior wall of the lesser sac....
- to transverse colonTransverse colonThe transverse colon, the longest and most movable part of the colon, passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath...
(occasionally on its own considered synonymous with "greater omentum") - Gastrosplenic ligamentGastrosplenic ligamentThe gastrosplenic ligament is part of the greater omentum.Embryonically the gastrosplenic ligament is derived from the dorsal mesogastrium....
- to spleenSpleenThe spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock... - Gastrophrenic ligamentGastrophrenic ligamentThe postero-inferior surface of the stomach is covered by peritoneum, except over a small area close to the cardiac orifice; this area is limited by the lines of attachment of the gastrophrenic ligament, and lies in apposition with the diaphragm, and frequently with the upper portion of the left...
- to thoracic diaphragmThoracic diaphragmIn the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
The splenorenal ligament
Splenorenal ligament
The splenorenal ligament , is derived from the peritoneum, where the wall of the general peritoneal cavity comes into contact with the omental bursa between the left kidney and the spleen; the lienal vessels pass between its two layers...
(from the left kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
to the spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
) is occasionally considered part of the greater omentum.
Blood Supply
The right and left gastroepiploic vesselsGastroepiploic artery
Gastroepiploic artery is the name of two different arteries serving the stomach and greater omentum:* Left gastro-omental artery, a branch of the splenic artery* Right gastro-omental artery, a branch of the gastroduodenal artery...
provide the sole blood supply to the greater omentum. Both are branches of branches off of the celiac trunk. The right gastroepiploic is a branch of the gastroduodenal artery
Gastroduodenal artery
In anatomy, the gastroduodenal artery is a small blood vessel in the abdomen.It supplies blood directly to the pylorus and proximal part of the duodenum, and indirectly to the pancreatic head .It most commonly arises from the common hepatic artery of the celiac trunk, but there are...
, which is a branch of the common hepatic artery
Common hepatic artery
In anatomy, the common hepatic artery is a short blood vessel that supplies oxygenated blood to the liver, pylorus , duodenum and pancreas....
, which is a branch of the celiac trunk. The left gastroepiploic artery is the largest branch of the splenic artery
Splenic artery
In anatomy, the splenic artery is the blood vessel that supplies oxygenated blood to the spleen. It branches from the celiac artery, and follows a course superior to the pancreas.-Branches:...
, which is a branch of the celiac trunk. The right and left gastroepiploic vessels anastomose within the two layers of the anterior greater omentum along the greater curvature of the stomach.
Development
The greater omentum develops from the dorsal mesenteryDorsal mesentery
The portion of mesentery attached to the greater curvature of the stomach is named the dorsal mesentery , and the part which suspends the colon is termed the mesocolon....
that connects the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
to the posterior abdominal wall. During stomach development, the stomach undergoes its first 90° rotation along the axis of the embryo, so that posterior structures are moved to the left and structures anterior to the stomach are shifted to the right. As a result, the dorsal mesentery folds over on itself, forming a pouch with its blind end on the left side of the embryo. A second approximately 90° rotation of the stomach, this time in the frontal plane, moves structures inferior if they were originally to the left of the stomach, and superior if they were originally to the stomach's right. Consequently, the blind-ended sac (also called the lesser sac
Lesser sac
The lesser sac, also known as the omental bursa, is the cavity in the abdomen that is formed by the lesser and greater omentum. Usually found in mammals, it is connected with the greater sac via the epiploic foramen...
) formed by the dorsal mesentery is brought inferiorly, where it assumes its final position as the greater omentum. It grows to the point that it covers the majority of the small and large intestine.
Omentectomy
Omentectomy refers to the surgical removal of the omentum, a relatively simple procedure with no major side effects, that is performed in cases where there may be spread of cancerous tissue into the omentum. Examples for this conditions are ovarian cancerOvarian cancer
Ovarian cancer is a cancerous growth arising from the ovary. Symptoms are frequently very subtle early on and may include: bloating, pelvic pain, difficulty eating and frequent urination, and are easily confused with other illnesses....
and advanced or aggressive endometrial cancer
Endometrial cancer
Endometrial cancer refers to several types of malignancies that arise from the endometrium, or lining, of the uterus. Endometrial cancers are the most common gynecologic cancers in the United States, with over 35,000 women diagnosed each year. The incidence is on a slow rise secondary to the...
as well as intestinal cancer. The procedure is generally done as an add-on when the primary lesion is removed.
See also
- PeritoneumPeritoneumThe peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
- Lesser omentumLesser omentumThe lesser omentum is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach and the start of the duodenum.- Structure :...
- Right gastroepiploic veinRight gastroepiploic veinThe right gastroepiploic vein drains into the superior mesenteric vein and drains venous blood from the lower parts of the antero-superior and posteroinferior surfaces of the stomach; it runs from left to right along the greater curvature of the stomach between the two layers of the greater omentum....
- Omental cakeOmental cakeIn radiology, omental cake is sign indicative of an abnormally thickened greater omentum. Typically, it is caused by infiltration of metastatic tumours arising from the stomach, ovary and colon. The appearance can also result from tuberculous peritonitis....
- Caul fatCaul fatCaul fat is the thin membrane which surrounds the stomach internal organs of some animals, such as hogs, cows, sheep, and pigs, also known as the greater omentum. It is often used as a natural sausage casing and to encase fegatelli , faggots , or pâté . Caul fat is also known as Lace...
- http://www.youtube.com/watch?v=sr3AAKd6Cb4&feature=related
