# Peritoneum

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Not to be confused with [Perineum](/source/Perineum).

"Peritoneal" redirects here. For other uses, see [Peritoneal (disambiguation)](/source/Peritoneal_(disambiguation)).

"Intraperitoneal" redirects here. For other uses, see [Intraperitoneal (disambiguation)](/source/Intraperitoneal_(disambiguation)).

The **peritoneum** is the [serous membrane](/source/Serous_membrane) forming the lining of the [abdominal cavity](/source/Abdominal_cavity) or [coelom](/source/Coelom) in [amniotes](/source/Amniote) and some invertebrates, such as [annelids](/source/Annelid). It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of [mesothelium](/source/Mesothelium) supported by a thin layer of [connective tissue](/source/Connective_tissue). This **peritoneal** lining of the cavity supports many of the [abdominal organs](/source/Abdomen#Contents) and serves as a conduit for their [blood vessels](/source/Blood_vessel), [lymphatic vessels](/source/Lymphatic_vessel), and [nerves](/source/Nerve).

The abdominal cavity (the space bounded by the [vertebrae](/source/Vertebrae), [abdominal muscles](/source/Abdominal_muscles), [diaphragm](/source/Thoracic_diaphragm), and [pelvic floor](/source/Pelvic_floor)) is different from 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](/source/Stomach) and [intestines](/source/Intestine)), the structures in the abdominal cavity that are located behind the intraperitoneal space are called "[retroperitoneal](/source/Retroperitoneal)" (e.g., the [kidneys](/source/Kidney)), and those structures below the intraperitoneal space are called "subperitoneal" or "infraperitoneal" (e.g., the [bladder](/source/Bladder)).

## Structure

### Layers

The peritoneum is one continuous sheet, forming two layers and a [potential space](/source/Potential_space) between them: the [peritoneal cavity](/source/Peritoneal_cavity).

The outer layer, the **parietal peritoneum**, is attached to the [abdominal wall](/source/Abdominal_wall) and the [pelvic walls](/source/Pelvic_walls).[1] The [tunica vaginalis](/source/Tunica_vaginalis), the serous membrane covering the male [testis](/source/Testis), is derived from the [vaginal process](/source/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](/source/Mesentery) is a double layer of visceral peritoneum that attaches to the [gastrointestinal tract](/source/Human_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 the parietal and visceral peritoneum is the [peritoneal cavity](/source/Peritoneal_cavity), filled with a small amount (about 50 mL) of slippery [serous fluid](/source/Serous_fluid) that allows the two layers to slide freely over each other.

The right [paracolic gutter](/source/Paracolic_gutter) is continuous with the right and left subhepatic spaces. The [epiploic foramen](/source/Epiploic_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 the [fallopian tubes](/source/Fallopian_tubes), the [uterus](/source/Uterus), and the [vagina](/source/Vagina).[3]

### Subdivisions

[Peritoneal folds](/source/Mesentery#Peritoneal_folds) are omentums, mesenteries and [ligaments](/source/Ligament); they connect organs to each other or to the abdominal wall.[4] There are two main regions of the peritoneal cavity, connected by the [omental foramen](/source/Omental_foramen).

- The [greater sac](/source/Greater_sac), represented in red in the diagrams above.
- The [lesser sac](/source/Lesser_sac), represented in blue. The lesser sac is divided into two "omenta": - The [lesser omentum](/source/Lesser_omentum) (or *hepatogastric*) is attached to the [lesser curvature of the stomach](/source/Lesser_curvature_of_the_stomach) and the [liver](/source/Liver).[5] - The [greater omentum](/source/Greater_omentum) (or *gastrocolic*) hangs from the [greater curvature of the stomach](/source/Greater_curvature_of_the_stomach) and loops down in front of the [intestines](/source/Intestines) before curving back upwards to attach to the transverse [colon](/source/Colon_(anatomy)).[5] In effect it is draped in front of the intestines like an apron and may serve as an insulating or protective layer.[5]

The [mesentery](/source/Mesentery) is the part of the peritoneum through which most abdominal organs are attached to the abdominal wall and supplied with [blood](/source/Blood) and [lymph](/source/Lymph) vessels and nerves.

#### [Omenta](/source/Omentum_(disambiguation))

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](/source/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 vein 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 Round ligament of uterus Uterus Inguinal canal Suspensory ligament of the ovary Ovary Pelvic wall Ovarian artery

In addition, in the [pelvic cavity](/source/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 and pelvic structures

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

Intraperitoneal Mesoperitoneal Retroperitoneal ( or Extraperitoneal ) Infraperitoneal / Subperitoneal Stomach, half of the first part of the duodenum [2.2 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) Spleen, pancreas (only tail) Liver Pancreas (except tail) Kidneys, adrenal glands, proximal ureters, renal vessels Urinary bladder, distal ureters Ovaries, uterine fundus and body (surrounded by the broad ligament) Gonadal blood vessels, uterine cervix, 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](/source/Mesoderm) of the [trilaminar embryo](/source/Trilaminar_embryo). As the mesoderm differentiates, one region known as the [lateral plate mesoderm](/source/Lateral_plate_mesoderm) splits to form two layers separated by an [intraembryonic coelom](/source/Intraembryonic_coelom). These two layers develop later into the visceral and parietal layers found in all [serous cavities](/source/Serous_cavity), including the peritoneum.

As an [embryo](/source/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.[6]

Peritoneal folds develop from the [ventral](/source/Ventral_mesentery) and [dorsal mesentery](/source/Dorsal_mesentery) of the embryo.[4]

## Clinical significance

### Imaging assessment

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]

### Peritoneal dialysis

Main article: [Peritoneal dialysis](/source/Peritoneal_dialysis)

In one form of [dialysis](/source/Kidney_dialysis), called **[peritoneal dialysis](/source/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](/source/Diffusion), waste products are removed from the blood.

### Peritonitis

Main article: [Peritonitis](/source/Peritonitis)

Peritonitis is the [inflammation](/source/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](/source/Gastric_acid) or [pancreatic juice](/source/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.[7]

### Primary peritoneal carcinoma

Main article: [Primary peritoneal carcinoma](/source/Primary_peritoneal_carcinoma)

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

## Etymology

"Peritoneum" is derived from Greek: περιτόναιον, *peritonaion*, lit. 'peritoneum, abdominal membrane'[8] via [Latin](/source/Latin). In Greek, none: περί, *peri* means "around", while none: τείνω, *teino* means "to stretch"; thus, "peritoneum" means "stretched over".[8]

## See also

- [Duodenorenal ligament](/source/Duodenorenal_ligament)
- [Omental bursa](/source/Omental_bursa) ([Lesser sac](/source/Lesser_sac))
- [Greater sac](/source/Greater_sac)
- [Omental foramen](/source/Omental_foramen) ([Epiploic foramen](/source/Epiploic_foramen), [Foramen of Winslow](/source/Foramen_of_Winslow))
- [Lesser omentum](/source/Lesser_omentum)
- [Greater omentum](/source/Greater_omentum)

## References

1. Tank PW (2013). ["Chapter 4: The abdomen"](https://books.google.com/books?id=JDC-dFMy-BIC&pg=PA99). *Grant's dissector*. Fifteenth ed. Philadelphia. ISBN 978-1-60913-606-2.

1. Jones, J. (14 April 2009). [*Epiploic Foramen | Radiopaedia.org*](https://radiopaedia.org/articles/epiploic-foramen-1#:~:text=The%20epiploic%20foramen%20(also%20called,communication%20between%20these%20two%20spaces.). Radiopaedia. [doi:10.53347/rID-6059](https://doi.org/10.53347/rID-6059). Retrieved 21 May 2022.

1. Tirkes, Temel; Sandrasegaran, Kumaresan; Patel, Aashish A.; Hollar, Margaret A.; Tejada, Juan G.; Tann, Mark; Akisik, Fatih M.; Lappas, John C. (March 2012). ["Peritoneal and Retroperitoneal Anatomy and Its Relevance for Cross-Sectional Imaging"](http://pubs.rsna.org/doi/10.1148/rg.322115032). *RadioGraphics*. **32** (2): 437–451. [doi:10.1148/rg.322115032](https://doi.org/10.1148/rg.322115032). [ISSN 0271-5333](https://www.worldcat.org/issn/0271-5333). [PMID 22411941](https://pubmed.ncbi.nlm.nih.gov/22411941)

1. Drake, R. L.; Vogl, A.W.; Mitchell, A.W. (4 April 2009). ["Abdominal Viscera"](https://books.google.com/books?id=_ozrqnzzhFwC&dq=These%20folds&pg=PA295). *Gray's Anatomy for Students*. Philadelphia, PA: [Elsevier Health Sciences](/source/Elsevier_Health_Sciences). p. 295. ISBN 9781437720556. [OCLC 489070574](https://www.worldcat.org/oclc/489070574)

1. Tortora GJ, Anagnostakos NP (1984). *Principles of anatomy and physiology*. 4th ed. New York: Harper & Row. ISBN 978-0-06-046656-5.

1. ["Peritoneum"](http://healthoracle.org/downloads/P/Peritoneum.pdf). *healthoracle.org*. [Archived](https://web.archive.org/web/20160423062639/http://healthoracle.org/downloads/P/Peritoneum.pdf) 23 April 2016 at the Wayback Machine. Retrieved 14 April 2018.

1. 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 978-0-07-174889-6.

1. ["Peritoneum - Origin and meaning of peritoneum by Online Etymology Dictionary"](http://www.etymonline.com/index.php?term=peritoneum). *www.etymonline.com*. Retrieved 14 April 2018.

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Adapted from the Wikipedia article [Peritoneum](https://en.wikipedia.org/wiki/Peritoneum) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Peritoneum?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.