Peritoneum

Infobox Anatomy
Name = Peritoneum
Latin =
GraySubject = 246
GrayPage = 1149

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Caption = The peritoneum, coloured in blue

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Caption2 = The epiploic foramen, greater sac or general cavity (red) and lesser sac, or omental bursa (blue). (Areas outlined in blue and red correspond to above diagram.)
System =
MeshName = Peritoneum
MeshNumber = A01.047.025.600
DorlandsPre = p_14
DorlandsSuf = 12629236
In higher vertebrates, the peritoneum is the serous membrane that forms the lining of the abdominal cavity — it covers most of the intra-abdominal organs. It is composed of a layer of mesothelium supported by a thin layer of connective tissue.The peritoneum both supports the abdominal organs and serves as a conduit for their blood and lymph vessels and nerves.

tructure

Layers

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). For example, a kidney is inside the abdominal cavity, but is retroperitoneal.

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.
* The inner layer, the visceral peritoneum, is wrapped around the internal organs that are located inside the intraperitoneal 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.
* 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. It should be noted that the space between these two layers is technically outside of the peritoneal sac, and thus not in the peritoneal cavity.

ubdivisions

There are two main regions of the peritoneum, connected by the epiploic foramen:

* the greater sac (or "general cavity of the abdomen"), represented in red in the diagrams above.
* the lesser sac (or "omental bursa"), represented in blue. The lesser sac is divided into two "omenta":
** The lesser omentum (or "gastrohepatic") is attached to the lesser curvature of the stomach and the liver.
** The greater omentum (or "gastrocolic") hangs from the greater curve of the stomach and loops down in front of the intestines before curving back upwards to attach to the transverse colon. In effect it is draped in front of the intestines like an apron and may serve as an insulating or protective layer.

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.

Structures include:

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.

Etymology

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

=Additional

References

*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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* [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/misc_topics/peritoneum.html Overview and diagrams at colostate.edu]