The greater omentum (also the great omentum, omentum majus, gastrocolic omentum, epiploon, or, especially in animals, caul) is a large apron-like fold of

visceral peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesothel ...

that hangs down from the stomach. It extends from the

greater curvature The curvatures of the stomach refer to the greater and lesser curvatures. The greater curvature of the stomach is four or five times as long as the lesser curvature. Greater curvature The greater curvature of the stomach forms the lower lef ...

of the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, passing in front of the small intestines and doubles back to ascend to the

transverse colon In human anatomy, the transverse colon is the longest and most movable part of the colon. Anatomical position It crosses the abdomen from the ascending colon at the right colic flexure (hepatic flexure) with a downward convexity to the descend ...

before reaching to the posterior

abdominal wall In anatomy, the abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the anterolateral and posterior walls. There is a common set of layers covering and forming all the walls: the deepest being the ...

. The greater omentum is larger than the

lesser omentum The lesser omentum (small omentum or gastrohepatic omentum) is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach, and to the first part of the duodenum. The lesser omentum is usually divided into th ...

, which hangs down from the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

to the

lesser curvature The curvatures of the stomach refer to the greater and lesser curvatures. The greater curvature of the stomach is four or five times as long as the lesser curvature. Greater curvature The greater curvature of the stomach forms the lower left ...

. 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. It is the first structure observed when the abdominal cavity is opened anteriorly (from the front).

Structure

The greater omentum is the larger of the two

peritoneal The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of meso ...

folds. It consists of a double sheet of peritoneum, folded on itself so that it has four layers. The two layers of the greater omentum descend from the greater curvature of the stomach and the beginning of the duodenum. They pass in front of the small intestines, sometimes as low as the pelvis, before turning on themselves, and ascending as far as the

, where they separate and enclose that part of the intestine. These individual layers are easily seen in the young, but in the adult they are more or less inseparably blended. The left border of the greater omentum is continuous with the

gastrosplenic ligament The gastrosplenic ligament (also known as the ''ligamentum gastrosplenicum'' or gastrolienal ligament) is part of the greater omentum extending between the stomach and the spleen. It contains several blood vessels. Structure The gastrosplenic li ...

; its right border extends as far as the beginning of the duodenum. The greater omentum is usually thin, and has a perforated appearance. It contains some

adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...

, which can accumulate considerably in

obese Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...

people. It is highly vascularised.

Subdivisions

The greater omentum is often defined to encompass a variety of structures. Most sources include the following three: *

Gastrophrenic ligament The postero-superior 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, ...

—extends to the underside of the left dome of the diaphragm *

Gastrocolic ligament The 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. Dividing the gastrocolic ligament provides access ...

—extends to the

(occasionally on its own considered synonymous with "greater omentum") *

Gastrosplenic ligament The gastrosplenic ligament (also known as the ''ligamentum gastrosplenicum'' or gastrolienal ligament) is part of the greater omentum extending between the stomach and the spleen. It contains several blood vessels. Structure The gastrosplenic li ...

(or Gastrolienal) ligament)— extends to the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

, overlying the kidney The splenorenal ligament (or lienorenal ligament) (from the left

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

to the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

) is occasionally considered part of the greater omentum. It is derived from the

peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of meso ...

, where the wall of the general peritoneal cavity comes into contact with the

lesser sac The lesser sac, also known as the omental bursa, is a part of the peritoneal cavity that is formed by the lesser and greater omentum. Usually found in mammals, it is connected with the greater sac via the omental foramen or ''Foramen of Winsl ...

between the left

and the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

; the

splenic artery In human anatomy, the splenic artery or lienal 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. It is known for its tortuous path to the s ...

and

vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenat ...

pass between its two layers. It contains the tail of the

pancreas The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an en ...

, the only intraperitoneal portion of the pancreas, and splenic vessels.

Phrenicosplenic ligament

The phrenosplenic ligament (lienophrenic ligament or phrenicolienal ligament) is a double fold of

that connects the

thoracic diaphragm The thoracic diaphragm, or simply the diaphragm ( grc, διάφραγμα, diáphragma, partition), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm is the m ...

and

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

. The phrenicosplenic ligament is part of the greater omentum. Distinctions between the phrenicosplenic ligament and adjacent ligaments, such as the gastrophrenic, gastrosplenic and splenorenal ligaments, which are all part of the same mesenteric sheet, are often nebulous.

Blood supply

The right and left gastroepiploic arteries (also known as gastroomental) provide the sole blood supply to the greater omentum. Both are branches of the celiac trunk. The right gastroepiploic artery is a branch of the

gastroduodenal artery In anatomy, the gastroduodenal artery is a small blood vessel in the abdomen. It supplies blood directly to the pylorus (distal part of the stomach) and proximal part of the duodenum. It also indirectly supplies the pancreatic head (via the anterio ...

, which is a branch of the

common hepatic artery The common hepatic artery is a short blood vessel that supplies oxygenated blood to the liver, pylorus of the stomach, duodenum, pancreas, and gallbladder. It arises from the celiac artery and has the following branches: Additional images ...

, which is a branch of the celiac trunk. The left gastroepiploic artery is the largest branch of the

, which is a branch of the celiac trunk. The right and left gastroepiploic arteries 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 mesentery that connects the

to the posterior abdominal wall. During its 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

) 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.

Functions

The functions of the greater omentum are: *Fat deposition, having varying amounts of

*Immune contribution, having milky spots of macrophage 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.

Clinical significance

Surgical removal

Omentectomy refers to the surgical removal of the omentum, a relatively simple procedure with no documented major side effects, that is performed in cases where there is concern that there may be spread of cancerous tissue into the omentum. Examples for this are

ovarian cancer Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...

and advanced or aggressive endometrial cancer as well as

intestinal cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel ...

and also appendix cancer. The procedure is generally done as an add-on when the primary lesion is removed.

Omental flap

The greater omentum may be surgically harvested for reconstruction of the

thoracic wall The thoracic wall or chest wall is the boundary of the thoracic cavity. Structure The bony skeletal part of the thoracic wall is the rib cage, and the rest is made up of muscle, skin, and fasciae. The chest wall has 10 layers, namely (from sup ...

. It has also been used experimentally to reinforce bioengineered tissues transplanted to the surface of the heart for cardiac regeneration.

Use in brain surgery

The greater omentum may be surgically harvested to provide revascularization of brain tissue after a stroke.

History

The greater omentum is also known as the great omentum, the omentum majus, the gastrocolic omentum, the epiploon, and the caul. In 1906, the greater omentum was described as the "abdominal policeman" by the surgeon James Rutherford Morrison. This is due to its immunological function, whereby omental tissue seems to "surveil" the abdomen for infection and cover areas of infection when found - walling it off with immunologically active tissue.

Additional images

File:Gray1035.png, Vertical disposition of the

. Main cavity, red; omental bursa, blue. (Greater omentum labeled at left.) File:Sobo 1909 565.png, The greater omentum is attached to the lower portion of the stomach (here the attachment is cut and the stomach is lifted up). File:Gray532.png, The celiac artery and its branches; the liver has been raised, and the lesser omentum and anterior layer of the greater omentum removed. File:Gray989.png, Schematic figure of the bursa omentalis, etc. Human embryo of eight weeks. File:Gray990.png, Diagrams to illustrate the development of the greater omentum and transverse mesocolon. File:Slide2DDE.JPG, Greater omentum. Deep dissection.

Notes and references

External links

* * * * * ()
Diagram at Tn.edu
* Photo of model at Waynesburg College
digirep/greateromentum
' * Learn about living without an Omentum at The Omentum Project: https://www.theomentumproject.org/ {{Authority control Abdomen

Structure

Subdivisions

Phrenicosplenic ligament

Blood supply

Development

Functions

Clinical significance

Surgical removal

Omental flap

Use in brain surgery

History

Additional images

See also

Notes and references

External links