Peritoneum

Not to be confused with Perineum.
Peritoneum

The peritoneum, colored in blue

The epiploic foramen, greater sac or general cavity (red) and lesser sac, or omental bursa (blue).
Details
Identifiers
Latin Peritoneum
MeSH A01.047.025.600
Code TH H3.04.08.0.00001
TA A10.1.02.002
FMA 9584

Anatomical terminology

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. 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

Types

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

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

Sources Structure From To Contains
Dorsal mesentery Greater omentum Greater curvature of stomach (and spleen) Transverse colon right and left gastroepiploic vessels and fat
Gastrosplenic ligament Stomach Spleen Short gastric artery, Left gastroepiploic artery
Gastrophrenic ligament Stomach Diaphragm Left inferior phrenic artery
Gastrocolic ligament Stomach Transverse colon Right gastroepiploic artery
Splenorenal ligament Spleen Kidney Splenic artery, Tail of pancreas
Ventral mesentery Lesser omentum Lesser curvature of the stomach (and duodenum)Liver 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.
Hepatogastric ligament Stomach Liver Right and left gastric artery
Hepatoduodenal ligament Duodenum Liver Hepatic artery proper, hepatic portal vein, bile duct, autonomic nerves

Mesenteries

Sources Structure From To Contains
Dorsal mesentery Mesentery proper Small intestine (jejunum and ileum) Posterior abdominal wall Superior mesenteric artery, accompanying veins, autonomic nerve plexuses, lymphatics, 100–200 lymph nodes and connective tissue with fat
Transverse mesocolon Transverse colon Posterior abdominal wall Middle colic
Sigmoid mesocolon Sigmoid colon Pelvic wall Sigmoid arteries and superior rectal artery
Mesoappendix Mesentery of ileum Appendix Appendicular artery

Other ligaments and folds

Sources Structure From To Contains
Ventral mesentery Falciform ligament Liver Thoracic diaphragm, anterior abdominal wall Round ligament of liver, paraumbilical veins
Left umbilical vein Round ligament of liver Liver Umbilicus
Ventral mesentery Coronary ligament Liver Thoracic diaphragm
Ductus venosus Ligamentum venosum Liver Liver
Phrenicocolic ligament Left colic flexure Thoracic diaphragm
Ventral mesentery Left triangular ligament, right triangular ligament Liver
Umbilical folds Urinary bladder
Ileocecal fold Ileum Cecum
Broad ligament of the uterus Uterus Pelvic wall Mesovarium, mesosalpinx, mesometrium
Ovarian ligament Uterus Inguinal canal
Suspensory ligament of the ovary Ovary Pelvic wall Ovarian 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:

Name Location Sexes possessing structure
Rectovesical pouch Between rectum and urinary bladder Male only
Rectouterine pouch Between rectum and uterus Female only
Vesicouterine pouch Between urinary bladder and uterus Female only
Pararectal fossa Surrounding rectum Male and female
Paravesical fossa Surrounding urinary bladder Male 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).

Intraperitoneal Retroperitoneal Infraperitoneal / 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 vessels Urinary bladder, distal ureters
In women: ovaries Gonadal 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.

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. 1 2 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.
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