The abdominal cavity (the space bounded by thevertebrae,abdominal muscles,diaphragm, andpelvic floor) is different from theintraperitoneal space (located within the abdominal cavity but wrapped in peritoneum). The structures within the intraperitoneal space are called "intraperitoneal" (e.g., thestomach andintestines), the structures in the abdominal cavity that are located behind the intraperitoneal space are called "retroperitoneal" (e.g., thekidneys), and those structures below the intraperitoneal space are called "subperitoneal" or "infraperitoneal" (e.g., thebladder).
The inner layer, thevisceral peritoneum, is wrapped around the visceral organs, located inside the intraperitoneal space for protection. It is thinner than the parietal peritoneum. Themesentery is a double layer of visceral peritoneum that attaches to thegastrointestinal tract. There are often blood vessels, nerves, and other structures between these layers. The space between these two layers is technically outside of the peritoneal sac, and thus not in the peritoneal cavity.
The potential space between these two layers is theperitoneal cavity, filled with a small amount (about 50 mL) of slipperyserous fluid that allows the two layers to slide freely over each other.
The rightparacolic gutter is continuous with the right and left subhepatic spaces. Theepiploic foramen allows communication between the greater sac and the lesser sac.[2] The peritoneal space in males is closed, while the peritoneal space in females is continuous with the extraperitoneal pelvis through openings of thefallopian tubes, theuterus, and thevagina.[3]
Peritoneal folds are omentums, mesenteries andligaments; they connect organs to each other or to the abdominal wall.[4] There are two main regions of the peritoneal cavity, connected by theomental foramen.
Thegreater sac, represented in red in the diagrams above.
Thelesser sac, represented in blue. The lesser sac is divided into two "omenta":
Thegreater omentum (orgastrocolic) hangs from thegreater curvature of the stomach and loops down in front of theintestines before curving back upwards to attach to the transversecolon.[5] In effect it is draped in front of the intestines like an apron and may serve as an insulating or protective layer.[5]
Themesentery is the part of the peritoneum through which most abdominal organs are attached to the abdominal wall and supplied withblood andlymph vessels and nerves.
The right free margin-hepatic artery, portal vein, and bile duct,lymph nodes and the lymph vessels,hepatic plexus of nerve,all enclosed in perivascular fibrous sheath. Along the lesser curvature of the stomach-left and right gastric artery,gastric group of lymph nodes and lyphatics, branches from gastric nerve.
In addition, in thepelvic cavity there are several structures that are usually named not for the peritoneum, but for the areas defined by the peritoneal folds:
The structures in the abdomen are classified as intraperitoneal, mesoperitoneal,retroperitoneal or infraperitoneal depending on whether they are covered with visceral peritoneum and whether they are attached by mesenteries (mensentery, mesocolon).
Structures that areintraperitoneal are generally mobile, while those that areretroperitoneal are relatively fixed in their location.
Some structures, such as the kidneys, are "primarily retroperitoneal", while others such as the majority of the duodenum, are "secondarily retroperitoneal", meaning that structure developed intraperitoneally but lost its mesentery and thus became retroperitoneal.
The peritoneum develops ultimately from themesoderm of thetrilaminar embryo. As the mesoderm differentiates, one region known as thelateral plate mesoderm splits to form two layers separated by anintraembryonic coelom. These two layers develop later into the visceral and parietal layers found in allserous cavities, including the peritoneum.
As anembryo develops, the various abdominal organs grow into the abdominal cavity from structures in the abdominal wall. In this process they become enveloped in a layer of peritoneum. The growing organs "take their blood vessels with them" from the abdominal wall, and these blood vessels become covered by peritoneum, forming a mesentery.[6]
CT scan is a fast (15 seconds) and efficient way in visualising the peritoneal spaces. Although ultrasound is good at visualizing peritoneal collections and ascites, without ionising radiation, it does not provide a good overall assessment of all the peritoneal cavities. MRI scan is also increasingly used to visualise peritoneal diseases, but requires long scan time (30 to 45 minutes) and prone to motion artifacts due to respiration and peristalsis and chemical shift artifacts at the bowel-mesentery interface. Those with peritoneal carcinomatosis, acute pancreatitis, and intraabdominal sepsis may not tolerate prolonged MRI scan.[3]
In one form ofdialysis, calledperitoneal dialysis, a glucose solution is sent through a tube into the peritoneal cavity. The fluid is left there for a prescribed amount of time to absorb waste products, and then removed through the tube. The reason for this effect is the high number of arteries and veins in the peritoneal cavity. Through the mechanism ofdiffusion, waste products are removed from the blood.
Peritonitis is theinflammation of the peritoneum. It is more commonly associated to infection from a punctured organ of the abdominal cavity. It can also be provoked by the presence of fluids that produce chemical irritation, such asgastric acid orpancreatic juice. Peritonitis causes fever, tenderness, and pain in the abdominal area, which can be localized or diffuse. The treatment involves rehydration, administration of antibiotics, and surgical correction of the underlying cause. Mortality is higher in the elderly and if present for a prolonged time.[7]
"Peritoneum" is derived fromGreek:περιτόναιον,romanized: peritonaion,lit. 'peritoneum, abdominal membrane'[8] viaLatin. In Greek,περί,peri means "around", whileτείνω,teino means "to stretch"; thus, "peritoneum" means "stretched over".[8]
^abcTortora GJ, Anagnostakos NP (1984).Principles of anatomy and physiology (4th ed.). New York: Harper & Row.ISBN978-0-06-046656-5.
^"Peritoneum"(PDF).healthoracle.org. Archived fromthe original(PDF) on 23 April 2016. Retrieved14 April 2018.
^Longo D, Fauci A, Kasper D, Hauser S, Jameson J, Loscalzo J (2012).Harrison's Principles of Internal Medicine (18th ed.). New York: McGraw-Hill. pp. 2518–2519.ISBN978-0-07-174889-6.
![Cytology of the normal mesothelial cells that line the peritoneum, with typical features.[9] Wright's stain](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aCytology_of_normal_mesothelium.jpg)
