Peritoneum 40583 225206427 2008-07-12T13:29:54Z Devil Master 97301 Peritonitis does not "refer to" an inflammation, peritonitis IS an inflammation! {{Infobox Anatomy | Name = Peritoneum | Latin = | GraySubject = 246 | GrayPage = 1149 | Image = Gray1040.png | Caption = The peritoneum, coloured in blue| Image2 = Greater_and_lesser_sac_1035.gif | 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 [[vertebrate]]s, the '''peritoneum''' is the [[serous membrane]] that forms the lining of the [[abdomen|abdominal cavity]] &mdash; 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]]. ==Structure== ===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 organ]]s 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 [[millilitre|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. ===Subdivisions=== 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 (anatomy)|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: {| class="wikitable" | '''SOURCES''' || '''STRUCTURE''' || '''FROM''' || '''TO''' || '''CONTAINS ''' |- | || '''[[omentum|OMENTA]]''' || || || |- | [[dorsal mesentery]] || * [[greater omentum]] || greater curvature of [[stomach]] (and [[spleen]]) || || |- | dorsal mesentery || ** [[gastrosplenic ligament]] || [[stomach]] || [[spleen]] || [[short gastric artery]], [[left gastro-omental artery]] |- | dorsal mesentery || ** [[gastrophrenic ligament]] || [[stomach]] || [[Thoracic diaphragm|diaphragm]] || - |- | dorsal mesentery || ** [[gastrocolic ligament]] || [[stomach]] || [[transverse colon]] || - |- | dorsal mesentery || ** [[splenorenal ligament]] || [[spleen]]|| [[kidney]] || [[splenic artery]], [[tail of pancreas]] |- | [[ventral mesentery]] || * [[lesser omentum]] || lesser curvature of the [[stomach]] (and [[duodenum]])|| || |- | ventral mesentery || ** [[hepatogastric ligament]] || [[stomach]] || [[liver]] || |- | ventral mesentery || ** [[hepatoduodenal ligament]] || [[duodenum]] || [[liver]] || [[hepatic artery proper]], [[hepatic portal vein]], [[bile duct]] |- | || '''[[mesenteries|MESENTERIES]]''' || || || |- | dorsal mesentery || * Mesentery proper || [[small intestine]] – [[jejunum]] and [[ileum]] || posterior [[abdominal wall]] || [[superior mesenteric artery]] |- | dorsal mesentery|| * [[transverse mesocolon]] || [[transverse colon]] || posterior [[abdominal wall]] || [[middle colic]] |- | dorsal mesentery || * [[sigmoid mesocolon]] || sigmoid colon || [[pelvic wall]] || [[sigmoid arteries]] |- | dorsal mesentery || * [[mesoappendix]] || mesentery of [[ileum]] || [[appendix]] || [[appendicular artery]] |- | || '''OTHER LIGAMENTS AND FOLDS''' || || || |- | 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: {| class="wikitable" | '''Name''' || '''Location''' || '''Genders 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 |} ==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 cavity|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. ==Clinical aspects== ===Pathology=== * [[Pneumoperitoneum]] is the presence of gas within the peritoneal cavity, as may occur when a perforation forms in the stomach or intestines, and heralds a perilous situation. * [[Peritonitis]] is an [[inflammation]] of the peritoneal lining or cavity, which may occur with either a perforation or by spread of infection through the wall of one of the abdominal organs. This too is a serious condition, and often requires emergency surgery. * [[Ascites]] is an accumulation of excess fluid within the peritoneal cavity. ===[[Peritoneal dialysis]]=== In one form of [[dialysis]], the '''[[peritoneal dialysis]]''', a glucose solution is run 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. ==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 have a mesentery or not. {| class="wikitable" | '''Intraperitoneal''' || '''Retroperitoneal''' || '''Infraperitoneal / Subperitoneal''' |- | [[Stomach]], First part of the duodenum [5 cm], [[jejunum]], [[ileum]] || The rest of the [[duodenum]] || |- | [[Cecum]], [[Vermiform appendix|appendix]], [[transverse colon]], [[sigmoid colon]] || [[Ascending colon]], [[descending colon]] |- | [[Rectum]], upper 1/3 || [[Rectum]], middle 1/3 || [[Rectum]], lower 1/3 |- | [[Pancreas]] (tail), [[liver]], [[spleen]] || [[Pancreas]] (head and body) || |- | || [[Kidney]]s, [[suprarenal gland]]s, [[ureter]]s, [[renal artery|renal vessels]] || [[Urinary bladder]], [[ureter]]s(end) |- | In women: [[Uterus]], [[Fallopian tube]]s, [[Ovary|ovaries]] || [[gonadal artery|Gonadal 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. ==Etymology== ''Peritoneum'' is derived from Greek. ''Peri-'' means ''around'', while ''-ton-'' refers to stretching. Thus, peritoneum means ''stretched around'' or ''stretched over''. ==Additional images== <gallery> Image:Illu bladder.jpg|Bladder Image:Gray403.png|Median sagittal section of pelvis, showing arrangement of fasciæ. Image:Gray1038.png|Horizontal disposition of the peritoneum in the lower part of the abdomen. Image:Gray1125.png|Sagittal section through posterior abdominal wall, showing the relations of the capsule of the kidney. Image:Gray1224.png|Topography of thoracic and abdominal viscera. Image:Gray1039.png|Horizontal disposition of the peritoneum in the upper part of the [[abdomen]] </gallery> ==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== * {{SUNYAnatomyLabs|37|03|01|02}} * [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/misc_topics/peritoneum.html Overview and diagrams at colostate.edu] {{Peritoneum}} [[Category:abdomen]] [[ar:بريتوان]] [[cs:Pobřišnice]] [[de:Peritoneum]] [[es:Peritoneo]] [[eo:Peritoneo]] [[fr:Péritoine]] [[it:Peritoneo]] [[la:Peritoneum]] [[lt:Pilvaplėvė]] [[nl:Buikvlies]] [[pl:Otrzewna]] [[pt:Peritônio]] [[sk:Pobrušnica]] [[sl:Potrebušnica]] [[fi:Vatsakalvo]] [[sv:Bukhinna]] [[zh:腹膜]]