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Omentum: Types, Functions, and Significance

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The omentum is a large, fat-filled layer of the peritoneum that covers the organs in the abdomen. Let us know more details in this article.

Written by

Dr. Janani R S

Medically reviewed by

Dr. Ghulam Fareed

Published At December 27, 2022
Reviewed AtFebruary 1, 2023

Introduction:

Omentum is a fatty tissue layer present as folds that are stuck together in the peritoneum. They attach to the abdominal organs like the stomach and intestines. The omentum plays a vital role in regulating metabolism, and immune response, stores fat, and plays a role in tissue regeneration (formation of new tissues).

What Is Omentum?

The omentum is a sheet of two layers of the peritoneum (a lining that covers the abdomen and pelvis) that are fused to form a covering that passes from the stomach and duodenum (the first part of the small intestine) to other organs in the abdominal cavity. The weight of the omentum varies from 300 grams (gm) to 2000 grams (gm).

What Are the Functions of the Omentum?

  • Immune Response: The omentum plays an essential role in the immune response of the peritoneal cavity. The omentum defends the invading organisms through a group of white blood cells that are present as milky dots. The white blood cells purify the abdominal fluids circulating within the abdominal cavity and the omentum. When an infectious organism is detected in the fluid, the milky spots become active and destroy the harmful microorganisms.

  • Fat Storage: The omentum stores vast amounts of fat. The fat deposits in the omentum are different from the fat deposited under the skin. The fat deposits in the omentum play an essential role in peritoneal immune regulation and contain mesenchymal stem cells that ease the growth of endometrial tumors.

  • Infection and Wound Isolation: The omentum covers the wounded or injured part and separates it from the healthy part. It prevents the spread of infection to other structures.

  • Protects Organs: It protects and holds the organs in the abdominal cavity.

  • Neovascularization: The omentum encourages new blood vessel formation in nearby structures. It heals and provides blood supply by forming new vessels in the injured or inflamed tissue.

  • Tissue Regeneration: Omentum is transported and placed to repair an injured organ due to its wound-healing capacity. Though the reasons for how it enables wound healing are unclear, it is widely used to form new tissue in the injured site.

What Are the Types of Omentum?

  • Greater Omentum: The Greater omentum contains a lot of fatty deposits. It is a bulky apron-like tissue that expands from the greater curvature of the stomach and proximal part of the duodenum (the first part of the small intestine). It goes down to the transverse colon (part of the large intestine), ileum, and jejunum. The ileum and jejunum are the middle and last parts of the small intestine. The apron-like tissue moves backward and upwards and attaches itself to the transverse mesocolon.

    • The gastro-omental arteries supply the greater omentum. The right gastro-omental artery is a division of the gastroduodenal artery. The left gastroduodenal artery arises from a structure called the splenic artery. The veins travel with the arteries and empties into the portal system.

    • Functions:

      • It prevents the lining of the anterior abdominal wall and innermost peritoneum of the ileum from joining together.

      • It wraps around the inflamed or infected organs and separates them from other healthy organs. Hence it is called the police force of the abdomen.

  • Lesser Omentum: The lesser omentum starts extending from the lesser curvature of the stomach and the first part of the duodenum (duodenal bulb) to the liver. The lesser omentum consists of a medially present hepatogastric ligament and a laterally present hepatoduodenal ligament. The hepatogastric ligament joins the lesser curvature of the stomach and the deeper part of the liver.

The hepatoduodenal ligament crosses the duodenal bulb to the deep surface of the liver. The hepatoduodenal ligament transports the hepatic portal vein, bile duct, and proper hepatic artery. The hepatic portal vein is a tubular structure that carries blood from the liver. The proper hepatic artery is a blood vessel that carries blood to the liver. The bile duct carries bile from the liver and gallbladder to the small intestine and pancreas.

  • Blood Supply: The lesser omentum carries blood supply to the lesser curvature of the stomach through the right and left gastric arteries. The left gastric artery crosses the lesser omentum and moves down in a left to right path together with the lesser curvature of the stomach. The right gastric artery, which is a bifurcation of the proper hepatic artery, moves upwards with the lesser curvature of the stomach in the right to left direction to join together with the left gastric artery. The right and left gastric veins travel in a similar path as the arteries along with the lesser omentum and empty into the hepatic portal vein.

  • Functions: It serves as a pathway for the blood vessels to enter the liver.

What Is Omentum Cancer?

Omentum is not subjected to cancer growth, but cancers of other organs in the peritoneal cavity, like ovarian cancer, spread to the omentum. The omentum not only acts as a police force of the abdomen but also allows the production of cancer cells in the milky spot. The milky spot plays a defense role during infections but is compromised when there is metastasis (spread of cancer from other sites). The cancer growth occurs in the omentum.

How Is Omentum Cancer Treated?

Surgical resection of the cancerous tumor, together with the omentum, is removed. However, in some cases, like ovarian cancer, it spreads to the omentum and other intraperitoneal organs. The main reason for eliminating omentum along with the cancerous growth is that it helps find the staging of the disease and helps assess if the patient is fit for chemotherapy.

What Is Omentoplasty?

Omentoplasty is a surgical procedure where the greater omentum is removed and placed in other areas of the body to reform a defect or dysfunction. For example, it is used in surgeries involving gastrointestinal conditions such as perforated peptic ulcers, gynecological hysterectomy (removal of the uterus), throat reconstruction, and revascularization surgeries (repairing and forming blood vessels), chest infections, and chest-wall reconstruction.

Conclusion:

The omentum is a vital fatty tissue that forms like a curtain covering the organs in the abdominal cavity. The parts of the omentum are greater and lesser omentum. They have beneficial functions like keeping the organs in place, helping form new blood vessels, protecting the organs from infection, and isolating them. In addition, it kills harmful organisms that invade the organs in the peritoneal cavity. However, it also has a few compromising effects, like metastasis. It does not defend against the invading cancer cells but, in turn, allows its growth in the omentum. Although the omentum in metastasis is compromised, it still protects the organs and promotes blood vessels and tissue regeneration, making it an essential and widely accepted replacement surgery.

Frequently Asked Questions

1.

What Happens on the Removal of the Omentum?

The removal of the omentum, a tissue covering abdominal organs, is called an omentectomy. Removal of it can cause retention of fluid and can cause blockage of lymphatic blood vessels. The person can also have difficulty in passing stools or urine. There is also an increased risk of nerve damage, infections, and bleeding if the person undergoes surgical treatment. 

2.

Explain Omentum and Its Location.

The omentum is a layer of fat tissue in the form of folds and is present together with the peritoneum (a layer that lines the abdominal cavity). It covers the intestine and stomach. It has two parts, the greater and lesser omentum. The greater omentum extends from the highest part of the stomach to the transverse mesocolon. The lesser omentum extends from the more secondary curved part of the stomach up to the first part of the duodenum.

3.

Explain the Functions of Omentum.

The functions of omentum are:
- Storage of a large number of fat.
- Prevention of spreading of infection to other parts by separating the injured part from the healthy part.
- Protects the abdominal organs.
- It helps provide an immune response with the help of white blood cells, which are present in the tissue as white spots.
- Helps in the formation of blood tissues.
- Helps in tissue regeneration.

4.

In What Cases Is Omentum Removed?

The omentum is removed when there is cancer in the omentum tissue. It can also be removed when cancer is present in nearby areas, such as ovarian cancer, prostate cancer, uterine cancer, stomach cancer, appendix cancer, and colorectal cancer, because these cancers can spread to other parts. Removing omentum can prevent it from spreading.

5.

Does Omentum Have Growing Potential after It Is Removed?

No, omentum has no growth potential. It is a fatty layer of tissue covering the abdominal organs. Once removed, indicated in case of a cancer in it or in other nearby place, it can not grow back. But it has the potential to heal wounds.

6.

Are Belly Fat and Omentum the Same?

Yes, belly fat is the same as omentum fat, a thick, fatty layer covering the stomach and intestines. It helps in the storage of fat, aids in tissue regeneration, and prevents the spread of cancer from adjacent areas. It also plays a vital role in immune response and regulation of metabolism. 
 

7.

Is Having an Omentum a Normal Condition?

Yes, the omentum is a thick layer of fat in folds. The omentum is like an apron that covers the stomach and intestine. It is present in every individual and is a normal thing. The omentum is attached to the peritoneum, a layer covering the abdominal cavity. 

8.

How Long Can a Person Survive with Omentum Tumor?

Omentum tumor is a rare type of cancer that can occur. The omentum should be removed in such cases, but the person can have difficulty passing waste products. The size of the tumor impacts the survival rate. In the case of untreated omentum, cancer, which can spread to other parts, has a poor survival rate of around six months.

9.

Explain women’s Omentum.

Every individual has an omentum rich in fat, stretching from the stomach to the large intestine. It is important in providing immunity and regulating metabolism. It has two parts called greater omentum and lesser omentum. In case of cancer in the omentum, it has to be removed.  
 

10.

How Large Is Omentum?

Omentum spreads from the highest stomach arch up to the large intestine. Its surface area can vary among individuals. It can weigh from 300 to 2000 grams (gm). Its surface area can range from 300 to 1500 cm2 (square centimeters).

11.

Can Omentum Be Symptomatic?

No, omentum cannot be symptomatic. If cancer starts in the omentum, the symptoms can be such as nausea, abdominal pain, constipation, and loss of appetite.  Apart from these, there can also be abdominal distention and weight loss. In such cases, an omentectomy is performed.

12.

Is Omentum the Same as Liver?

No, the omentum is different from the liver. The omentum is a tissue layer extending from the stomach to the intestine. At the same time, the liver is an organ in the abdominal region. The inner layer of the omentum called the lesser omentum, spreads from the inferior stomach arch up to the intestine and covers the liver.
 

13.

Explain Greater Omentum.

The greater omentum is the outermost layer of the omentum, which contains a large amount of fats. It extends from the highest stomach arch up to the large intestine. It prevents the spread of infection to other parts. It receives blood supply from the greater omentum, a part of the gastroduodenal artery.

14.

Explain the Ligaments of the Greater Omentum.

It has three ligaments: gastrocolic, gastrosplenic, and gastrophrenic. The gastrocolic ligament extends up to the transverse colon. The gastrophrenic ligament extends up to the thoracic diaphragm. The gastrosplenic ligament extends up to the spleen.
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Dr. Ghulam Fareed
Dr. Ghulam Fareed

Medical Gastroenterology

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