What is Peritoneum?

The Peritoneum meaning can be better understood as we define peritoneum as the membrane that lines many organs in the body. Peritoneum meaning is better explained as it is a serous membrane that forms the lining of the abdominal cavity or coelom which is the main body cavity in most animals. And the peritoneum is positioned inside the body to surround the organs that contain the digestive tract in the coelom and it also lines the other organs. The coelomic organs are also referred to as the intra-abdominal organs. The peritoneum is supported by a thin layer of connective tissue over the mesothelium cells layer lining. The physiology of the peritoneum is not just limited to a membrane lining it serves many purposes. Now that we have understood what is peritoneum let us understand the various roles the peritoneum meaning caters to in location and function.

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Anatomy of the Peritoneum

Peritoneum Location- The Peritoneum membrane location is very important to note as it wraps up the abdominal cavity,  and the abdominal cavity is an open space. And that is surrounded by the vertebrae, abdominal muscles, diaphragm, and pelvic floor. the visceral organs and many organs that exist within the membrane and even behind it. The peritoneal location can be understood in three ways. 


Intraperitoneal Organs

Retroperitoneal Organs

Infraperitoneal Organs

For this kind of organs, the peritoneum completely surrounds it and hence is called intraperitoneal as the organs lie within it.

As the peritoneum covers the abdominal organs the organs that lie behind having been covered by the peritoneum on the hind part are called the retroperitoneal organs. 

It is also called the subperitoneal organs. It mainly refers to the tissues that are deep into the peritoneum. These organs are also included within the extraperitoneal space

Such organs are the stomach, spleen, liver, all parts of the small intestine that is the duodenum, jejunum and ileum, uterus, fallopian tubes, ovaries, appendix, caecum and the transverse and sigmoid colon. 

The retroperitoneal organs can be divided into two ways the primary retroperitoneal organs are the kidneys, rectum and oesophagus. And the ascending and descending colon,  pancreas, ureter and suprarenal glands located on the kidneys are the secondary retroperitoneal organs.

Gonadal bood vessels, the lower part of the rectum, the distal ureters and the urinary bladder. 


The Peritoneum Membrane - It is a layer of mesothelial cells that are surrounded by supportive connective tissue and it consists of two layers; the outer layer called outer parietal layer and the inner layer that is the inner visceral layer. Both are composed of the same tissues and yet they have very different stimuli and physiological functions. 

Layers of Peritoneum Membrane


Outer Parietal Peritoneum Layer 

Inner Visceral Peritoneum Layer

  • The outer parietal layer is hitched to the pelvic wall and the abdominal walls. 

  • The inner surface of the abdominopelvic cavity walls is lined by the parietal layer.

  • The somatopleuric layer of the lateral plate mesoderm is the precursor to the derivative of the peritoneum layer. 

  • It is sensitive to pain as it is innervated by the somatic nerves. 

  • The tunica vaginlis , an outpouching of the parietal peritoneum derived from the vaginal process, is a serous membrane that covers the testis in males. 

  • The mesentery is the double layer of the visceral peritoneum attached to the gastrointestinal tract. 

  • Forms the wall serosa in the visceral parts.

  • The serosa of the visceral peritoneum covers the outer surface of some of the abdominal viscera and pelvic viscera.

  • The visceral peritoneum protects due to the peritoneum location inside the intraperitoneal space.

  • The autonomic nerves innervate the visceral peritoneum making pain insensitive. 


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The Peritoneum Membrane Development

The mesoderm is the origin of the peritoneum membrane development. From the trilaminar embryo of the mesoderm, the peritoneal membrane is formed. The first stage of development- It is when the intraembryonic coelom separates and splits the lateral plate of the mesoderm into two layers the mesoderm starts to differentiate. 


The two layers of the differentiated mesoderm then start developing into the two layers in the serous cavities. The layers that are known as the outer layer called the parietal peritoneum layer and the inner visceral layer. The two layers are the components of the developed peritoneum. 


As an embryo develops, in the initial stages within the abdominal wall the various abdominal organs grow into the abdominal cavity from structures. And during this developmental process, the organs in the abdomen become enveloped in a layer of peritoneum membrane. The growing organs very organically "take their blood vessels with them" with them as there is no growth without blood supply from the abdominal wall. And mesentery the double layer within the inner visceral layer of the peritoneum is formed as it covers the blood vessels. 

What is Peritoneal Cavity?

Peritoneal Cavity- The peritoneal cavity is the peritoneal space between the separated area of the two layers of the peritoneum. The peritoneal cavity is bound by thin membranes and it is basically between the organ structures that the peritoneum covers or lines. It is an open space surrounded by the vertebrae and other abdominal parts. 

The folds of the peritoneum are called Omentum and these folds occur due to their association with the stomach in the gastrointestinal tract. There are two kinds of omentum: the greater omentum and the lesser omentum. Omentum also participates and aids the peritoneum function in the body. The greater omentum descends from the greater curvature of the stomach and proximal part of the duodenum, which are the first and the second fold of the greater omentum then folds back up making it the third layer and follows by attaching to the anterior surface of the transverse colon which is the fourth layer making it four layers of the greater omentum. The lesser omentum, on the other hand, is a double layer that attaches from the stomach’s lesser curvature to the proximal part of the duodenum following the liver. The lesser omentum is further divided into two kinds: the flat, broadsheet called the hepatogastric ligament and the free edge, which contains the portal triad called the hepatoduodenal ligament. The peritoneal cavity has two subdivisions which can be called the Larger Greater Sac and the Smaller Lesser Sac. 

Two Subdivisions Peritoneal Cavity


Greater Sac

Lesser Sac

As the name suggests it is the larger part of the peritoneal cavity. 

It is also known as the omental bursa and as the name suggests it is smaller in size as it is a diverticulum of the larger greater sac. 

It extends from the diaphragm below the abdomen to the pelvis region. 

Located behind the lesser omentum and the stomach. 

The transverse mesocolon that is the mesentery of the transverse colon into two parts the supracolic compartment that lies above it and the infracolic compartment below it. By the mesentery of the small intestine, the inferior infracolic compartment is divided into two left and right infracolic spaces. The paracolic gutters which lie between the posterolateral abdominal wall and the lateral aspect of the ascending or descending colon connect the supracolic and infracolic compartments.

The lesser sac communicates via the epiploic foramen of Winslow that is situated posterior to the free edge of the lesser omentum in the hepatoduodenal ligament with the greater sac. 

The supracolic compartment contains the liver, spleen and stomach whereas the small intestine, ascending and descending colon is in the infracolic compartment. 

It functions by allowing the stomach to move freely. The movement of the stomach is uninterrupted against the structures posterior and inferior to it.


Peritoneum Function

  1. The peritoneum covers nearly all visceral organs within the gut in the abdominal area and it functions by conveying neurovascular structures to the intraperitoneal viscera from the body wall. 

  2. Acts as a conduit for the passage of blood vessels, lymphatics and nerves.

  3. Supports the organs of the abdomen.

  4. The omentum provides visceral mobility. 

  5. The folds that are the omentum also function as a pathway for the nerves and other blood vessels.

  6. The damage of the organs during any rough movements is prevented by providing lubrication via the secretion of peritoneal fluid into the peritoneal cavity by the peritoneum.

  7. Fat storage is aided by the peritoneum.

  8. The healing of wounds and protecting from damage to the organs as the mesothelial cells of the peritoneum transform themselves into fibroblasts.

  9. The phagocytic cells in the peritoneum membrane protect the visceral organs by guarding against any kinds of infections.

  10. Due to the physicality of the greater omentum in the stomach, it can wrap around an infected area and that limits the spread of any intraperitoneal infections within the body.

  11. The omentum connects the abdomen to the viscera inside the body.

  12. Due to the high number of arteries and veins in the peritoneal cavity, it serves as a great medium within the system to help in the clinical way of dealing with peritoneal dialysis.

  13. The greater omentum can migrate to any part of the infected viscera and even any site of surgical disturbances and acts as a form of the immune mechanism and therefore is referred to as the ‘abdominal police’.

Peritoneum Damage and Problems

The peritoneum travels and is connected through many organs and when any damage or problem arises there is a high probability of it spreading through the peritoneal cavity and other organs that it is associated through the intraperitoneal layer, retroperitoneal layer or the supra peritoneal layer.

  • When there is portal hypertension then there is excess secretion of the peritoneal fluid within the peritoneal cavity which leads to Ascites. This abnormal build-up of fluid can be life-threatening when it leads to infection.

  • Peritonitis is the inflammation of the peritoneum when one is undergoing peritoneal dialysis therapy. 

  • The cancer of the cells lining the peritoneum leads to primary peritoneal carcinoma.

Conclusion

The Peritoneum protects and helps the body moving and going through many changes and when it is damaged the results can be fatal. One must not ignore any symptoms or signs of the possibility of a problem. Preservation of this important membrane is very important and the ways one can do so is by having high-quality protein and avoiding foods with high amounts of sodium and phosphorus and avoiding canned foods, chillies etc. One is responsible for their own health and a good diet is an important part of it so one can help themselves by consulting a nutritionist. Peritoneal health is as necessary as any other organ as it protects all organs it covers. 

FAQs (Frequently Asked Questions)

Q.1) Is Mesentery a Part of the Peritoneum Membrane?

Ans.) The mesentery is very much a part of the peritoneum membrane which has two layers outer parietal and inner visceral. The inner visceral peritoneum layer has a double-layered mesentery and regardless of how the mesentery is classified, it is important to note that it is an essential part of the human body. The mesentery is integral to the health of the gastrointestinal tract and the intestines. The removal of the entire mesentery is not possible if it creates interruption due to an illness or an injury, while parts of the mesentery may be removed depending on the severity and after considering all the possible treatments and must be done only if recommended by the doctor.  

Q.2) What is the Location of the Mesentery in the Human Body?

Ans.) The mesentery of the peritoneum is found in your abdomen. In the abdomen, the mesentery of the visceral layer surrounds your intestines. The mesentery emerges from the backside of the abdomen where the aorta branches off to another large artery. This artery in the mesentery is called the superior mesenteric artery.

Q.3) Can One Survive Upon the Removal of the Peritoneum?

Ans.) The removal of the peritoneum is only considered when there is a danger of damage to the body because of it. The mesothelial layer is the main component of the peritoneum membrane which can often cause peritoneal mesothelioma that increases chances of cancer and in that case, only the affected part of the entire membrane of the peritoneum layer is removed. The possibility of surgery is to be decided upon by the experts. And the procedure is called peritonectomy. This means removing part or all of the lining of the peritoneum in the abdomen, usually highly probable for mesothelioma. The main aim of the surgery is to reduce symptoms and further damage.

Q.4) Does Water Intake Treat Ascites?

Ans.) The treatment of ascites can be aided with the help of diuretics, less intake of salts and water. In case there is an infection due to excess fluid in the ascites condition one must immediately consult a doctor and not rely on any other information except the experts.