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07.09.04 (4 years ago)
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The Peritoneum and the Peritoneal Cavity
The peritoneum is a thin, transparent serous membrane that consists of two layers.
The peritoneum lining the abdominal wall is called the parietal peritoneum.
The peritoneum investing the viscera is called the visceral peritoneum.
Both types of peritoneum consist of a single layer of squamous epithelium (mesothelium).
The parietal and visceral layers of peritoneum are separated from each other by capillary films of peritoneal fluid.
This serous fluid lubricates the peritoneal surfaces, enabling the viscera to move on each other without friction.
When an organ protrudes into the peritoneal sac, it takes its vessels and nerves with it.
They are located between to two layers of peritoneum and form the mesentery.
There is also loose connective tissue between these layers that contains a variable amount of fat cells.
Viscera with mesentery are mobile, the degree to which depends on the length of mesentery.
As the developing organs enlarge, they obliterate the peritoneal cavity almost completely.
As the foetal organs assume their adult positions, the peritoneal cavity is divided into two peritoneal sacs, the greater and lesser sacs of the peritoneum.
A surgical incision through the anterior abdominal wall enters the greater peritoneal sac.
The lesser sac, known as the omental bursa, lies posterior to the stomach, lesser omentum and liver.
The peritoneal cavity is closed in males.
In females, there is a communication with the exterior through the uterine tubes, uterus and vagina
Descriptive Terms
Mesentery
This is a double layer of peritoneum that encloses the organ and connects it to the abdominal wall.
Mesenteries have a core of loose connective tissue containing a variable number of fat cells and lymph nodes along with nerves and vessels passing to and from the viscera.
The mesentery of the stomach is called the mesogastrium (G. gaster, stomach).
The mesentery of the transverse colon is the transverse mesocolon.
The mesentery of the small intestine is the mesentery.
Some visceral have no mesentery and are extraperitoneal or retroperitoneal (e.g., the ascending colon and kidneys).
These organs lie on the posterior abdominal wall and are covered by peritoneum anteriorly.
The liver develops in the ventral mesogastrium.
The spleen develops in the dorsal mesogastrium.
Omentum
This is a double-layered sheet or fold of peritoneum.
The lesser and greater omentum attach the stomach to the body wall or to other abdominal organs.
The Lesser Omentum
This fold of peritoneum connects the lesser curvature of the stomach and the proximal part of the duodenum to the liver.
Individually, these connections are referred to as the gastrohepatic ligament and the hepatoduodenal ligament.
The lesser omentum lies posterior to the left lobe of the liver and is attached to the liver in the fissure for the ligamentum venosum.
It is also attached to the porta hepatis, the transverse fissure or gate (L. porta) on the inferior surface of the liver through which the bile duct, vessels, and nerves enter or leave the liver.
The Greater Omentum
This is a fat-laden fold of peritoneum that hangs down from the greater curvature of the stomach and connects the stomach with the diaphragm, spleen, and transverse colon.
This double-layered peritoneal fold normally fuses during the foetal period, thereby obliterating the inferior recess of the omental bursa.
As a result, the apron-like greater omentum is composed of four layers of peritoneum.
After passing inferiorly as far as the pelvis, the greater omentum loops back on itself, overlying and attaching to the transverse colon.
Vertical disposition of the peritoneum. Main cavity, red; omental bursa, blue.
Horizontal disposition of the peritoneum in the upper part of the abdomen.
Horizontal disposition of the peritoneum in the lower part of the abdomen.
Subdivisions of the Peritoneal Cavity
The greater omentum, along with the transverse colon and the transverse mesocolon, forms a shelf that subdivides the peritoneal cavity into supracolic and infracolic compartments.
The Omental Bursa
The omental bursa (lesser sac of the peritoneum) is the large compartment or recess of the peritoneal cavity that is located between the stomach and the posterior abdominal wall.
The omental bursa is also located posterior to the lesser omentum and stomach.
The anterior and posterior walls of the bursa slide freely during contraction and distension of the stomach, giving it considerable freedom.
The inferior extension of the omental bursa is called the inferior recess.
It is the duplicated layers of the gastrocolic ligament of the greater omentum.
In adults, the inferior recess of the omental bursa is a potential space.
It is usually shut off from the rest of the bursa owing to adhesion of the layers of the gastrocolic ligament.
The omental bursa also has a superior recess.
This is limited superiorly by the diaphragm and the posterior layers of the coronary ligament.
The omental bursa is in communication with the main peritoneal cavity through the omental foramen (epiploic foramen or foramen of Winslow).
This is located posterior to the free edge of the lesser omentum.
The omental foramen is usually large enough to admit two digits.
Boundaries of the Omental Foramen
Anteriorly: the portal vein, hepatic artery, and bile duct (all in the free edge of the lesser omentum).
Posteriorly: the inferior vena cava and right crus of the diaphragm.
Superiorly: the caudate lobe of the liver.
Inferiorly: the superior part of the duodenum, portal vein, hepatic artery and bile duct
Peritoneal Ligaments
A peritoneal ligament is a double layer of peritoneum that connects an organ with another organ or with the abdominal wall.
Ligaments may contain blood vessels or remnants of vessels (e.g., the falciform ligament contains the ligamentum teres, a remnant of the foetal umbilical vein).
The greater omentum is divided into 3 parts:
The apron-like part, called the gastrocolic ligament, is attached to the transverse colon.
The left part, called the gastrosplenic ligament (gastrolienal ligament), connects the hilum of the spleen to the greater curvature and fundus of the stomach.
The superior part called the gastrophrenic ligament is attached to the diaphragm and the posterior aspect of the fundus and the oesophagus.
The falciform ligament extends from the liver to the anterior abdominal wall and the diaphragm.
The ligamentum teres is the obliterated remnant of the left umbilical vein, lying in the free edge of the falciform ligament and extending from the groove for the ligamentum teres to the umbilicus.
The superior (anterior) and inferior (posterior) layers of the coronary ligament are reflections of the peritoneum, which surround the bare area of the liver.
The left and right triangular ligaments are where the layers of the coronary ligament meet to the left and right respectively.
The falciform, coronary and triangular ligaments are derived from that part of the ventral mesogastrium connecting the liver to the body wall.
The gastrohepatic and hepatoduodenal ligaments are derived from that part of the ventral mesogastrium connecting the stomach and the liver.
The gastrosplenic and gastrophrenic, as well as the lienorenal and phrenicolienal ligaments are derived from the dorsal mesogastrium.
The Peritoneal Folds
A peritoneal fold (L. plica) is a reflection of peritoneum with more or less sharp borders.
Often it is formed by peritoneum that covers blood vessels, ducts, and obliterated foetal vessels.
Several folds are visible on the parietal peritoneum on the interior of the anterior abdominal wall.
The median umbilical fold contains the urachus, which extends from the urinary bladder to the umbilicus.
The medial umbilical folds are raised by the obliterated umbilical arteries, extending from the internal iliac arteries to the umbilicus.
The lateral umbilical folds are raised by the inferior epigastric arteries, extending from the deep inguinal rings on each side to the arcuate lines.
Peritoneal Pouches
The rectouterine pouch (in females) separating the rectus from the bladder.
The rectovesical pouch (in males) separating the rectum from the bladder.
The vesicounterine pouch (in females) separating the bladder from the uterus
Blood Supply of the Peritoneum
To the parietal peritoneum
Lumbar vessels
Branches of the inferior and superior epigastric arteries
Musculophrenic artery
Deep circumflex arteries
To the visceral peritoneum
From the arteries supplying the appropriate viscera
Nerve Supply to the Peritoneum
To the parietal peritoneum
From the nerves supplying the adjacent body wall and diaphragm
To the visceral peritoneum
Sympathetic nerves innervating the appropriate visceral
The receptors are sensitive to:
Overdistension of the hollow viscera
Traction on the mesenteries which stretch the nerve plexus in the wall of the organ or mesentery
Spasm of smooth muscle
Ischæmia (inadequate blood supply)
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