Anatomy of Peritoneum in a Nutshell

Anatomy of Peritoneum

Overview of major organs: GI tract enters abdominal cavity at end of esophagus→pierces diaphragm to enter the stomach→ duodenum→jejunum→ilium→ascending colon→transverse colon→descending colon→sigmoid colon→rectum.

Accessory organs: liver, gall bladder, and pancreas.  Develop embryologically from the digestive tract.

All of these organs are covered with visceral peritoneum.  Abdominal wall is lined with parietal peritoneum.

Peritoneum: a large, thin, transparent sheet of serous membrane which lines the walls of the abdominopelvic cavity and is reflected onto the viscera.

• Parietal peritoneum = lines the abdominal and pelvic walls
• Visceral peritoneum = covers abdominal and pelvic organs
• Peritoneal cavity = potential space between adjacent layers, usually contains only a small amount of fluid.

Most of the organs are anchored to the posterior abdominal wall.  The stalk that connects the organs to the wall = mesentery (not really either particular part of peritoneum).  Within this mesentery stalk, have artery (part of aorta) and vein (part of portal system).

Peritoneal cavity:

• Subdivided by the greater and lesser omentum into two sacs
  • Greater sac
  • Lesser sac, AKA omental bursa.
  • The omental foramen (epiploic foramen) connects the 2 sacs.
• Closed in males.
• Communicates with exterior in femalesà communication with exterior provides exposure to foreign antigens, thus allowing more immunity (and subsequently lower occurrence of infection).

Mesentery:

• Double layer of peritoneum that connects an intraperitoneal organ to the posterior abdominal wall.
• Has a connective tissue core in which blood vessels, nerves, and lymphatics travel to and from the intraperitoneal organ.
• Organs within a mesentery are freely movable.

Intraperitoneal organs:

• Covered with visceral peritoneum except at sites where mesentery attaches
• Examples: small intestine, spleen.
• Mesentery of small intestine = “the mesentery”.
• Thus, if it has a mesentery, it is intraperitoneal.

Retroperitoneal (extraperitoneal) organs:

• Not covered with visceral peritoneum on one or more sides.
• Do not have a mesentery.
• Primarily retroperitoneal:
  • Always behind peritoneum
  • Kidneys are primary retroperitoneal.
• Secondarily retroperitoneal
  • Some organs they started out as intraperitoneal, but with development, they lost their mesentery
  • Ascending / descending colon and pancreas.
  • These are fixed on abdominal wall.

Omentum: double layer of peritoneum attached to the stomach and proximal part of duodenum.

• Lesser Omentum:
  • Attaches the stomach (along the lesser curvature) to the liver.
  • Subdivided into 2 ligaments = hepatogastric and hepatoduodenal ligaments.

• • • Hepatogastric: From liver to stomach
    • Hepatoduodenal:
      1. This is thicker as it contains the bile duct, hepatic artery, and the portal vein.
      2. Behind this ligament, will find the omental foramen, allows communication between greater / lesser sacs.

• Greater Omentum:
  • Attaches the stomach (along the greater curvature) to the posterior abdominal wall.
  • Subdivided into 3 ligaments = gastrophrenic, gastrosplenic, gastrocolic ligaments.  These describe attachments (i.e. stomach to diaphgram).
  • The gastrosplenic ligament of the greater omentum:

1. 1. • Is between the stomach and the spleen, is a much smaller division of the greater omentum.
      • The gastrophrenic ligament anchors the fundus of the stomach to the diaphragm.

1. • The lesser sac is continuous with the space between the two layers of the greater omentum.
   • The greater omentum = “policeman”, will seal off infected portions in the abdomen.  Will create adhesions to organs or to abdominal wall in order to isolate infections.

Peritoneal ligaments: double layer of peritoneum which connect organs to organs or organs to body wall, e.g. gastrophrenic / hepatoduodenal ligaments.

Embryology:

• Above stomach: have both ventral and dorsal mesentery.
• Below stomach, only have dorsal mesentery.
• As growth occurs:
  • Tube becomes longer than cavity allows, and thus grows out into yolk sac.  It will later come back into the embryo from the yolk sac.  Curving and rotation occurs.
  • The greater omentum of the stomach grows out and over the intestines as a protective layer. This is specifically the gastrocolic ligament portion.
• From stomach to anterior abdominal wall = ventral mesentery.
  • Liver developed from this, part remains as falciform ligament.
  • At the base of this = old umbilical vein = ligamentum teres.

The lesser sac:

• A portion is found between the layers of the greater omentum gastrocolic ligament.
• The inferior recess of the lesser sac is that portion which is in the gastrocolic ligament.
• Also has recess posterior to liver = superior recess.
• Is behind the stomach.

The greater sac:

• Has the subphrenic recess which is between the liver and the diaphragm.
• It ends where peritoneum reflects onto diaphragm.
  • This reflection = coronary ligaments (superior / inferior).
  • The inferior coronary ligament represents the superior border of the superior recess of the lesser sac.
• Splenorenal ligament and gastrosplenic ligament separate greater / lesser sacs.

Excess fluid (when laying on back) will collect in the hepatorenal pouch which is near the kidney.

Peritoneal folds:

• A ridge on the surface of the body wall covered with parietal peritoneum.
• The ridge is produced by an underlying vessel, duct, or obliterated fetal vessel.
• 5 folds on body wall:
  1. Lateral umbilical folds: (2) inferior epigastric vessels.
  2. More inferiorly: medial umbilical folds : (2) obliterated umbilical artery.
  3. Median umbilical fold: urachus (singular)

Peritoneal recesses or fossa: a pouch of peritoneum formed by peritoneal folds or ligaments.

• 2 Fossa in body:
  • Rectovesical pouch (or female rectouterine pouch) = in the pelvic cavity.
  • Hepatorenal pouch
• Flow of fluid in these areas is through peritoneal gutters.
  • The attachments of the mesentery as well as the positions of the ascending and descending colon to the posterior abdominal wall form 4 gutters
  • Can conduct materials (blood, ascites, infection, bile) to other regions of the peritoneal cavity
  • Right and Left Paracolic gutters
  • Right and Left Infracolic gutters (AKA infracolic spaces)
• The transverse colon is the boundary between the Supracolic compartment and the infracolic conpartment.
• Fluid in the supracolic comparment will drain into the R paracolic gutter.

Also read:

Also Watch: