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Peritoneum


Source: http://en.wikipedia.org/wiki/Peritoneum
Updated: 2017-05-09T22:21Z
Not to be confused with Perineum.
"Peritoneal" redirects here. It is not to be confused with Perineal or Peroneal.
Peritoneum
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The peritoneum, colored in blue
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The epiploic foramen, greater sac or general cavity (red) and lesser sac, or omental bursa (blue).
Details
Identifiers
LatinPeritoneum
MeSHA01.047.025.600
CodeTH H3.04.08.0.00001
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Anatomical terminology
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The peritoneum /ˌpɛrtəˈnəm/ is the serous membrane that forms 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 mesothelium supported by a thin layer of connective tissue. This peritoneal lining of the cavity supports many of the abdominal organs and serves as a conduit for their blood vessels, lymphatic vessels, and nerves.

The abdominal cavity (the space bounded by the vertebrae, abdominal muscles, diaphragm, and pelvic floor) should not be confused with the intraperitoneal space (located within the abdominal cavity, but wrapped in peritoneum). The structures within the intraperitoneal space are called "intraperitoneal" (e.g., the stomach and intestines), the structures in the abdominal cavity that are located behind the intraperitoneal space are called "retroperitoneal" (e.g., the kidneys), and those structures below the intraperitoneal space are called "subperitoneal" or "infraperitoneal" (e.g., the bladder).

Structure

Types

Although they ultimately form one continuous sheet, two layers of peritoneum and a potential space between them are referenced:

  • The outer layer, the parietal peritoneum, is attached to the abdominal wall and the pelvic walls.[1] The tunica vaginalis, the serous membrane covering the male testis, is derived from the vaginal process, an outpouching of the parietal peritoneum.
  • The inner layer, the visceral peritoneum, is wrapped around the visceral organs, located inside the intraperitoneal space for protection. It is thinner than the parietal peritoneum.
  • The mesentery is a double layer of visceral peritoneum that attaches to the gastrointestinal 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 the peritoneal cavity; it is filled with a small amount (about 50 mL) of slippery serous fluid that allows the two layers to slide freely over each other.

Subdivisions

Peritoneal folds are omenta, mesenteries and ligaments; they connect organs to each other or to the abdominal wall.[2] There are two main regions of the peritoneal cavity, connected by the epiploic foramen (also known as the omental foramen or foramen of winslow):

The mesentery is the part of the peritoneum through which most abdominal organs are attached to the abdominal wall and supplied with blood and lymph vessels and nerves.

Omenta

SourcesStructureFromToContains
Dorsal mesenteryGreater omentumGreater curvature of stomach (and spleen)Transverse colonright and left gastroepiploic vessels and fat
Gastrosplenic ligamentStomachSpleenShort gastric artery, Left gastroepiploic artery
Gastrophrenic ligamentStomachDiaphragmLeft inferior phrenic artery
Gastrocolic ligamentStomachTransverse colonRight gastroepiploic artery
Splenorenal ligamentSpleenKidneySplenic artery, Tail of pancreas
Ventral mesenteryLesser omentumLesser curvature of the stomach (and duodenum)LiverThe 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.
Hepatogastric ligamentStomachLiverRight and left gastric artery
Hepatoduodenal ligamentDuodenumLiverHepatic artery proper, hepatic portal vein, bile duct, autonomic nerves

Mesenteries

SourcesStructureFromToContains
Dorsal mesenteryMesentery properSmall intestine (jejunum and ileum)Posterior abdominal wallSuperior mesenteric artery, accompanying veins, autonomic nerve plexuses, lymphatics, 100–200 lymph nodes and connective tissue with fat
Transverse mesocolonTransverse colonPosterior abdominal wallMiddle colic
Sigmoid mesocolonSigmoid colonPelvic wallSigmoid arteries and superior rectal artery
MesoappendixMesentery of ileumAppendixAppendicular artery

Other ligaments and folds

SourcesStructureFromToContains
Ventral mesenteryFalciform ligamentLiverThoracic diaphragm, anterior abdominal wallRound ligament of liver, paraumbilical veins
Left umbilical veinRound ligament of liverLiverUmbilicus
Ventral mesenteryCoronary ligamentLiverThoracic diaphragm
Ductus venosusLigamentum venosumLiverLiver
Phrenicocolic ligamentLeft colic flexureThoracic diaphragm
Ventral mesenteryLeft triangular ligament, right triangular ligamentLiver
Umbilical foldsUrinary bladder
Ileocecal foldIleumCecum
Broad ligament of the uterusUterusPelvic wallMesovarium, mesosalpinx, mesometrium
Ovarian ligamentUterusInguinal canal
Suspensory ligament of the ovaryOvaryPelvic wallOvarian artery

In addition, in the pelvic cavity there are several structures that are usually named not for the peritoneum, but for the areas defined by the peritoneal folds:

NameLocationSexes possessing structure
Rectovesical pouchBetween rectum and urinary bladderMale only
Rectouterine pouchBetween rectum and uterusFemale only
Vesicouterine pouchBetween urinary bladder and uterusFemale only
Pararectal fossaSurrounding rectumMale and female
Paravesical fossaSurrounding urinary bladderMale and female

Classification of abdominal structures

The structures in the abdomen are classified as intraperitoneal, retroperitoneal or infraperitoneal depending on whether they are covered with visceral peritoneum and whether they are attached by mesenteries (mensentery, mesocolon).

IntraperitonealRetroperitonealInfraperitoneal / Subperitoneal
Stomach, First part of the duodenum [5 cm], jejunum, ileum, cecum, appendix, transverse colon, sigmoid colon, rectum (upper 1/3)The rest of the duodenum, ascending colon, descending colon, rectum (middle 1/3)Rectum (lower 1/3)
Liver, spleen, pancreas (only tail)Pancreas (except tail)
Kidneys, adrenal glands, proximal ureters, renal vesselsUrinary bladder, distal ureters
In women: ovariesGonadal blood vessels, Uterus, Fallopian Tubes
Inferior vena cava, aorta

Structures that are intraperitoneal are generally mobile, while those that are retroperitoneal 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.

Development

The peritoneum develops ultimately from the mesoderm of the trilaminar embryo. As the mesoderm differentiates, one region known as the lateral plate mesoderm splits to form two layers separated by an intraembryonic coelom. These two layers develop later into the visceral and parietal layers found in all serous cavities, including the peritoneum.

As an embryo 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.[citation needed]

Peritoneal folds develop from the ventral and dorsal mesentery of the embryo.[2]

Clinical significance

Peritoneal dialysis

Main article: Peritoneal dialysis

In one form of dialysis, called peritoneal 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 of diffusion, waste products are removed from the blood.

Peritonitis

Main article: Peritonitis

Peritonitis is the inflammation 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 as gastric acid or pancreatic 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.[3]

Primary peritoneal carcinoma

Primary peritoneal cancer is a cancer of the cells lining the peritoneum.

History

Etymology

Peritoneum is derived from Greek via Latin. Peri- means around, while -ton- refers to stretching. Thus, peritoneum means stretched around or stretched over.

Additional images

References

  1. ^ Tank, P. (2013) Grants Dissector 15th ed., ch.4 The abdomen, p.99
  2. ^ a b Drake et al. (2009) Grays Anatomy for Students, 2nd Edition, Abdominal Viscera, p.406
  3. ^ 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. ISBN 978-0071748896. 
  • Tortora, Gerard J., Anagnostakos, Reginald Merryweather, Nicholas P. (1984) Principles of Anatomy and Physiology, Harper & Row Publishers, New York ISBN 0-06-046656-1

External links

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