Peritoneum

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Peritoneum
Gray1040.png
The peritoneum, coloured in blue
Gray1035.png
The epiploic foramen, greater sac or general cavity (red) and lesser sac, or omental bursa (blue).
LatinPeritoneum
Gray'sp.1149
MeSHPeritoneum
CodeTH H3.04.08.0.00001
Dorlands
/Elsevier
Peritoneum
 
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Not to be confused with Perineum.

Peritoneum
Gray1040.png
The peritoneum, coloured in blue
Gray1035.png
The epiploic foramen, greater sac or general cavity (red) and lesser sac, or omental bursa (blue).
LatinPeritoneum
Gray'sp.1149
MeSHPeritoneum
CodeTH H3.04.08.0.00001
Dorlands
/Elsevier
Peritoneum

The peritoneum /ˌpɛrɨtənˈiəm/ 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. The peritoneum supports the abdominal organs and serves as a conduit for their blood vessels, lymph 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), 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[edit]

Types[edit]

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

Subdivisions[edit]

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 peritoneum, 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[edit]

SourcesStructureFromToContains
Dorsal mesenteryGreater omentumGreater curvature of stomach (and spleen)Transverse colonright and left gastroepiploic vessels and fat
Gastrosplenic ligamentStomachSpleenShort gastric artery, Left gastro-omental artery
Gastrophrenic ligamentStomachDiaphragmLeft inferior phrenic artery
Gastrocolic ligamentStomachTransverse colonRight gastro-omental 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[edit]

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[edit]

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[edit]

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: uterus, fallopian tubes, ovariesGonadal blood vessels
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[edit]

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[edit]

Peritoneal dialysis[edit]

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.

Primary peritoneal carcinoma[edit]

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

History[edit]

Etymology[edit]

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[edit]

References[edit]

  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

External links[edit]