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Peritoneum

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Peritoneum

Not to be confused with Perineum.

Peritoneum
The peritoneum, coloured in blue
The epiploic foramen, greater sac or general cavity (red) and lesser sac, or omental bursa (blue).
Details
Latin Peritoneum
Identifiers
Gray's p.1149
MeSH A01.047.025.600
Code TH H3.04.08.0.00001
Dorlands
/Elsevier
Peritoneum
TA [1]
FMA FMA:9584
Anatomical terminology

The peritoneum is the 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 types or layers of peritoneum and a potential space between them are referenced:

  • The outer layer, called the parietal peritoneum, is attached to the abdominal wall and the pelvic walls.[1]
  • The inner layer, the visceral peritoneum, is wrapped around the internal organs that are located inside the intraperitoneal space. It is thinner than the parietal peritoneum.
  • 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.
  • The term mesentery is often used to refer to a double layer of visceral peritoneum. 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.

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 peritoneum, connected by the epiploic foramen (also known as the omental foramen or foramen of winslow):

The 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 gastro-omental artery
Gastrophrenic ligament Stomach Diaphragm Left inferior phrenic artery
Gastrocolic ligament Stomach Transverse colon Right gastro-omental 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

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

Clinical significance

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

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
  • 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

  • Anatomy photo:37:03-0102 at the SUNY Downstate Medical Center
  • Overview and diagrams at colostate.edu
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