No. 8

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No. 8

• 1. Peritoneum

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Chapter 6 The Peritoneum
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?. Introduction of Peritoneum

• The peritoneum is the largest and most complexly
  arranged serous membrane in the body. It consists
  of a single layer of flattened mesothelial cells
  which covers a layer of loose connective tissue.
  Its free surface is extremely smooth and slippery.

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• Parietal peritoneum and visceral peritoneum
• The peritoneum is situated in the abdominal
  cavity and partly also in the pelvic cavity, a
  part of which lines the wall and is known as the
  parietal peritoneum, while the remainder is
  reflected over the contained viscera and is
  termed the visceral peritoneum.

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• Peritoneal cavity
• The parietal and visceral layers of the
  peritoneum are in actual contact the potential
  space between them is the peritoneal cavity which
  contains nothing but a little lubricating fluid.
• In the male, the peritoneal cavity is a closed
  sac, in the female, it communicates with the
  exterior indirectly through the uterine tubes,
  uterus, and vagina.

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• Functions
• The peritoneum, especially the parietal
  peritoneum, has an absorptive capacity. After
  abdominal and pelvic operations, it has been
  customary to prop up the patient in bed so that
  any inflammatory intraperitoneal effusion will
  gravitate into the pelvis.
• One presumed reason for adopting this position
  was that the peritoneum in the subphrenic region
  has a greater absorptive capacity than the other
  regions hence inflammatory products, if they
  gained access to this region, would more rapidly
  pass into the general circulation.
• The visceral peritoneum is firmly united to the
  viscera which it covers, and cannot be readily
  stripped off them.

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?. The Relationship Between Viscera and Peritoneum

• According to the variable extent of peritoneal
  investment, the abdominopelvic viscera may be
  categorized into following three groups

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?) The Intraperitoneal Viscera

• Viscera completely surrounded by peritoneum that
  forms an integral part of serous layer belong to
  this group.
• Such organs are stomach, jejunum, ileum, cecum,
  vermiform appendix, transverse colon, sigmoid
  colon, spleen, ovaries, uterine tubes and
  superior part of the duodenum.

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?) The Interperitoneal Viscera

• Such organs are not completely wrapped by
  peritoneum with one surface attached to the
  abdominal walls or other organs.
• Liver, gallbladder, urinary bladder, uterus,
  upper part of the rectum, ascending and
  descending colon are the organs of this group.

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?) The Retroperitoneal Viscera

• Some of the abdominal and pelvic visera, such as
  the kidneys, ureters, suprarenal glands,
  pancreas, the middle part of rectum, the second
  and inferior parts of duodenum are
  retroperitoneal in position lying on the
  posterior abdominal wall and covered by
  peritoneum only on their anterior aspect.

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?. The Peritoneal Reflections

• Certain terms, often arbitrary, are commonly used
  for the peritoneal reflections.
• A peritoneal reflection that connects the
  intestine and body wall is usually named
  according to the part of the gut to which it is
  attached.
• For example, the reflection to jejunum and ileum
  is termed the mesentery, that to the transverse
  colon is the transverse mesocolon.
• Some peritoneal reflections between organs or
  between the body wall and organs, are termed
  ligaments or folds. Most of such ligaments or
  folds contain blood vessels. Broad peritoneal
  sheets associated with stomach are termed omenta.

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?) The Omentum

• There are two omenta, the lesser and the greater

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1. The lesser omentum

• It is the fold of peritoneum which extends to the
  liver from the lesser curvature of the stomach
  and the commencement of the duodenum.
• It is continuous with the two layers which cover
  the anterorsuperior and posteroinferior surfaces
  of the stomach and about the first 2 cm of the
  duodenum.
• The hepatogastric ligament and the hepatoduodenal
  ligament
• The portion of the lesser omentum extending
  between the liver and stomach is named the
  hepatogastric ligament, and that between the
  liver and duodenum the hepatoduodenal ligament.

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• Three key structures in the hepatoduodenal
  ligament
• At the right border of the hepatoduodenal
  ligament the two layers are continuous, and form
  a free margin which is the anterior wall of the
  epiploic foramen. In the free margin the two
  layers of the hepatoduodenal ligament enclose the
  proper hepatic artery, hepatic portal vein and
  common bile duct (These three structures are
  called three key structures in the hepatoduodenal
  ligament), a few lymph nodes and lymph vessels,
  and the hepatic plexus of nerves.
• The common bile duct is situated anteriorly, the
  hepatic portal vein posteriorly and the proper
  hepatic artery is at the left of the common bile
  duct. The inferior vena cava lies behind the
  epiploic foramen.

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2. The greater omentum

• It is the largest peritoneal fold. It consists of
  a double sheet, folded on itself so that it is
  made up of four layers.
• The two layers which descend from the stomach and
  commencement of the duodenum pass downwards in
  front of the small intestine for a variable
  distance they then turn up on the back of
  itself, and ascend to the transverse colon, where
  the two layers are separated to cover the
  anterior and posterior surfaces of transverse
  colon. Then they form the transverse mesocolon.

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• The upper part of the greater omentum which
  extends between the stomach and the transverse
  colon is termed the gastrocolic ligament.
• In adult, the four layers of greater omentum are
  frequently adhered together, and are found
  wrapped about the organs in the upper part of the
  abdomen only occasionally are they evenly
  dependent anterior to the intestines.

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• Functions
• ? protective function The greater omentum
  contains numerous fixed macrophages, which
  performs an important protective function.
• ? storehouse for fat The greater omentum is
  usually thin, and presents a cribriform
  apperarance, but always contains some adipose
  tissue, which in fatty people is present in
  considerable quantity.
• ? migration and limation The greater omentum may
  limit spread of infection in the peritoneal
  cavity. Because it will migrate to the site of
  any inflammation in the peritoneal cavity and
  wrap itself around such a site, the greater
  omentum is commonly referred to as the
  policeman of the peritoneal cavity.

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?) The Mesenteries and Mesocolons

• 1. The mesentery (of the small intestine)
• It is a broad, fan-shaped fold of peritoneum
  connecting the coils of jejunum and ileum to the
  posterior abdominal wall.
• The portion attached to the posterior wall of the
  abdomen is called the radix (root ) of mesentery
  it is about 15 cm long and is directed obliquely
  downwards from the duodenojejunal flexure (at the
  left side of the second lumbar vertebra) to the
  upper part of the right sacroiliac joint.

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• The intestinal border of the mesentery is about 6
  m and is thrown into numerous pleats and frills.
• The mesentery consists of two layers of the
  peritoneum between which lie the jejunal and
  ileal branches of the superior mesenteric artery
  with their accompanying veins, nerve plexuses and
  lymph vessels, the mesenteric lymph nodes,
  connective tissue and fat.

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• 2. The mesoappendix
• It is a triangular mesentery of the vermiform
  appendix, and is attached to the back of the
  lower end of the mesentery of ileum, close to the
  ileocecal junction.
• Its layers enclose the blood vessels, nerves and
  lymph vessels of the vermiform appendix, together
  with a lymph node.

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• 3. The transverse mesocolon
• It is a broad fold which connects the transverse
  colon to the anterior border of the pancreas.
  Between the layers of the transverse mesocolon
  are the blood vessels, nerves and lymphatics of
  the transverse colon.

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• 4. The sigmoid mesocolon
• It is a fold of peritoneum which attaches the
  sigmoid colon to the pelvic wall.
• The sigmoid and superior rectal vessels run
  between the layers of the sigmoid mesocolon, and
  the left ureter descends into the pelvis behind
  its apex.

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?) The Ligaments

• 1. The ligaments of the liver
• ? The falciform ligament of liver
• ? The ligamentum teres hepatis
• ? The coronary ligament
• ? The right triangular ligament
• ? The left triangular ligament
• ? The hepatogastric ligament
• ? The hepatoduonedenal ligament

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• 2. The ligaments of the spleen
• ? The splenorenal ligament The splenic
  vessels pass between its two layers.
• ? The gastrosplenic ligament The short
  gastric and left gastroepiploic branches of the
  splenic vessels run between its two layers.

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• 3. The ligaments of the stomach
• ? The gastrohepatic ligament
• ? The gastrocolic ligament
• ? The gastrosplenic ligament

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• 4. The suspensory ligament of duodenum
• Sometimes named Treitz ligament.
• 5. The phrenicocolic ligament
• It is a fold of peritoneum which is continued
  from the left colic flexure to the diaphragm
  opposite the tenth and eleventh ribs.

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?. The Peritoneal Recesses

• In certain parts of the abdomen, peritoneal fold
  may bound recesses or fossae of the peritoneal
  cavity.
• These recesses are of surgical importance since
  they may become the site of internal herniae,
  that is, a piece of intestine may enter a recess
  and may be constricted (strangulated) by the
  peritoneal fold granding the entrance to the
  recess.
• From a surgical point of view the omental bursa
  can be considered to belong to this category,
  with its opening at the epiploic foramen, bounded
  in front by the free border of the lesser omentum.

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?) The Omental Bursa

• It is a part of the peritoneal sac and almost
  closed off from the remainder.
• Location
• It lies behind the stomach and lesser omentum and
  has a small opening, the epiploic foramen, just
  above the first part of the duodenum.

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• Formation
• (1) The anterior wall of the omental bursa is
  formed by
• ? the posterior layer of lesser omentum,
• ? the peritoneum which covers the
  posteroinferior aspect of the stomach and about
  the first 2 cm of the duodenum,
• ? the posterior surface of the anterior two
  layers of the greater omentum.

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• (2) The posterior wall is formed by
• ? the anterior one of the posterior two
  layers of the greater omentum
• ? the peritoneum which lines the transverse
  colon, the transverse mesocolon, the pancreas,
  the left kidney and the left suprarenal gland.

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• The upper recess of the omental burse is roofed
  over by the diaphragm.
• The inferior recess of the bursa is limited by
  the lower border of the greater omentum, but, as
  a rule, partial fusion of the constituent layers
  of the greater omentum occurs after birth, so
  that the cavity of the omental bursa in the adult
  does not usually extend much below the transverse
  colon and its mesocolon.

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• (3) The omental bursa is limited to the left
  by the spleen and its peritoneal reflections, the
  splenorenal and the gastrosplenic ligaments.
• (4) On the right side, the omental bursa
  communicates with the greater peritoneal sac
  through the epiploic foramen.

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?) The Omental (Epiploic) Foramen (foramen of
Winslow)

• Location
• It lies between the liver and duodenum, just
  above the first part of the duodenum, is a short,
  vertically flattened passage, about 3 cm long,
  which leads out from the upper part of the right
  border of the omental bursa into the greater
  peritoneal sac.

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• Formation
• (1) Its anterior wall is formed by the right
  margin of the lesser omentum, which contains
  between its two layers in this situation the
  common bile duct, the hepatic portal vein and the
  proper hepatic artery.
• (2) The roof of the epiploic foramen is the
  peritoneum covering the inferior of the caudate
  lobe of the liver.
• (3) Its posterior wall is the peritoneum
  descending in front of the inferior vena cava.
• (4) The floor of the epiploic foramen is
  limited by the upper border of the superior part
  of the duodenum.

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?) The Other Recesses (of much smaller size)

• They are sometimes found in relation to the
  duodenum, cecum and sigmoid colon.
• They are sometimes found in relation to the
  duodenum, cecum and sigmoid colon.

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• 1. Duodenal Recesses
• The superior duodenal recess
• The inferior duodenal recess
• The paraduodenal recess
• The duodenojejunal recess
• 2. Cecal recesses
• The superior ileocecal,
• The inferior ileocecal
• The retrocecal recesses
• The rectocolic recess
• 3. The intersigmoid recess

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?) Pouches

• In the lesser pelvis, the peritoneum dips
  downwards forming a larger fossa, named pouch.

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1. In the male

• The rectovesical pouch lies between rectum and
  urinary bladder (or the seminal vesicles and
  ampullae ductus deferentes).
• The rectovesical pouch is the lowest part of the
  peritoneal cavity in anatomical position in male.

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2. In the female

• The uterus and its broad ligaments divide the
  rectovesical pouch into two pouches, the
  rectouterine pouch (of Douglas) and the
  vesicouterine pouch.
• (1) The rectouterine pouch is formed between
  the anterior surface of the rectum and the
  posteriosurface of the uterus and the upper part
  of vagina.
• (2) The vesicouterine pouch is formed between
  the anteroinferior surface of the uterus and the
  posterior surface of the urinary bladder.

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• The rectouterine pouch is the lowest part of the
  peritoneal cavity in anatomical position in the
  female.
• With a patient propped in the semi-sitting
  posture, the fluid in the peritoneal cavity may
  descend either to the relatively accessible
  rectovesical pouch or to the rectouterine pouch
  which may be approached surgically through the
  rectum or vagina.

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?. Subdivision of Peritoneal Cavity

• The greater sac is subdivided by the greater
  omentum, transverse colon, and transverse
  mesocolon into a superoanterior part, the
  supramesocolic compartment, and an
  inferoposterior part, the inframesocolic
  compartment.
• These compartments form channels or recesses that
  determine how or where peritoneal fluid
  gravitates or spreads.

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• The inframesocolic compartment is further divided
  by mesentery of small intestine into right and
  left parts.
• The latter drains into the pelvis.
• The paracolic grooves are longitudinal
  depressions lateral to the ascending and
  descending colon.
• The supramesocolic compartment is subdivided by
  the liver into subphrenic and subhepatic spaces.