Peritoneum and Abdominal Cavity

Peritoneum and Abdominal Cavity

• The peritoneum is a membrane (loose connective tissue) that forms a sac-like serous cavity.
• It lines the abdominopelvic cavity and surrounds abdominal organs.
• It consists of two continuous layers:
  • Parietal peritoneum: lines the internal surface of the abdominopelvic cavity.
  • Visceral peritoneum: covers the organs (viscera).

Relationship of Viscera to Peritoneum

• Intraperitoneal organs: Almost completely covered by the visceral peritoneum; they are not inside the peritoneum, but invaginated into a closed sac. Examples include the stomach, spleen, and small intestine.
• Extraperitoneal organs: Located outside the peritoneum, partially covered by it. An example is the kidneys.

Peritoneal Cavity

• A potential space between the parietal and visceral peritoneum.
• Contains peritoneal fluid, which reduces friction between the layers during organ movement.

Mesentery

• A double layer of peritoneum.
• Attaches organs to the posterior abdominal wall.
• Serves as a continuation of the visceral and parietal peritoneum.
• Provides a pathway for neurovascular communication between the organ and body wall.
• Examples of organs connected by mesentery include the jejunum, ileum, transverse colon, sigmoid colon, and appendix.

Omentum

• A double layer of peritoneum that forms folds attaching the stomach and proximal duodenum to adjacent organs in the abdominal cavity.
• Two types: greater and lesser.
  • Greater omentum: A large, apron-like fold extending from the greater curvature of the stomach and parts of the duodenum, covering parts of the small and large intestines. It folds back to attach to the anterior surface of the transverse colon.
  • Lesser omentum: A smaller fold connecting the stomach and duodenum to the liver.

Innervation

• Sensory innervation: from the phrenic nerve (inferior surface of the diaphragm), intercostal nerves, and subcostal nerve.
• Parietal peritoneum innervation: innervated from the abdominal cavity's other parts.

Peritoneal Formations

• Falciform ligament, hepatogastric, hepatoduodenal ligaments
• Portal triad containing the hepatic portal vein, hepatic artery, and common bile duct.
• Gastrophrenic, gastrosplenic, gastrocolic, and splenorenal ligaments
• Ligaments are folds of peritoneum attaching organs or structures to other organs or tissues, aiding in stabilizing their positions.

Peritoneal Folds

• Raised structures created by peritoneum reflecting over underlying structures like blood vessels and ducts.
• Lateral umbilical folds: contain inferior epigastric arteries.
• Median umbilical fold: contains the urachus.
• Medial umbilical folds: contain obliterated umbilical arteries.

Pouches and Recesses

• Pouches: Formed by peritoneal folds
• Duodenal recess
• Caecal recesses: superior, inferior, retrocecal
• Intersigmoid recess
• Omental bursa: A pouch-like structure posterior to the stomach, lesser omentum, and adjacent structures.

Omental Foramen (Epiploic Foramen)

• A small opening connecting the greater and lesser sacs of the peritoneal cavity.
• Boundaries: anterior (hepatoduodenal ligament), posterior (IVC and right crus of diaphragm), superior (caudate lobe of liver), inferior (1st part of the duodenum and common hepatic artery).

Division of Abdominal Cavity

• Supracolic compartment: Located superior to the transverse mesocolon and containing the stomach, spleen, and liver.
• Infracolic compartment: Located inferior to the transverse mesocolon and containing the small intestine and ascending/descending colon. Divided into left and right infracolic spaces.

Paracolic Gutters

• Channels in the abdominal cavity between the ascending/descending colon and the parietal peritoneum, enabling communication between supracolic and infracolic compartments.
• Right paracolic gutter extends to the inferior margin, no exit; the Left paracolic gutter extends to the inferior margin with an exit.