Peritoneum: Anatomy and Physiology

Peritoneum: Anatomy and Physiology

Nolan R. King, MD

Table of Contents

Peritoneum
Omentum
Mesentery
Retroperitoneum

Peritoneum

Peritoneum: A Bidirectional Semipermeable Membrane Lining the Abdominal Cavity

Physiology 

  • Absorbs Blood and Fluid Through Lymphatics
  • Made of Simple Squamous Epithelium

Layers

  • Visceral Peritoneum: Inner Layer Covering the Abdominal Organs
  • Parietal Peritoneum: Outer Layer Covering the Abdominal Wall

Visceral Peritoneum

  • Covers the Stomach, Small Intestine, Liver, Spleen, and Transverse Colon
  • Few Nerve Fibers – Poor Pain Localization
  • The Omentum and Mesentery are Folds of Visceral Peritoneum
  • Blood Supply: Splanchnic Vessels

Parietal Peritoneum

  • Covers the Abdominal Wall, Pelvis, and Diaphragm
  • Blood Supply: Intercostals, Subcostals, Lumbar, and Iliac Vessels
  • White Line of Toldt – Lateral Reflections of Parietal Peritoneum Along the Sides of the Ascending and Descending Colon

Peritoneal Cavity: The Potential Space Between the Two Layers – Normally Filled with Minimal Serous Fluid (50 cc)

Horizontal Cross-Section of the Abdomen and Peritoneal Covering (Red)

Omentum

Omentum: Large Folds of Visceral Peritoneum Containing Adipose Tissue

Structures

  • Lesser Omentum: Hangs off the Lesser Curvature of the Stomach
  • Greater Omentum: Hangs off the Greater Curvature of the Stomach

Lesser Omentum

  • Also Known as the “Gastrohepatic Omentum”
  • Hangs Down from the Liver to the Lesser Curvature of the Stomach and Duodenum
  • Contains Multiple Ligaments:
    • Hepatogastric Ligament – Liver to Stomach
    • Hepatoduodenal Ligament – Liver to Duodenum
  • Blood Supply: Right and Left Gastric Arteries

Greater Omentum

  • Also Known as the “Gastrocolic Omentum”
  • Extends From the Greater Curvature of the Stomach to Cover the Small Intestine Before Doubling Back and Ascending to the Transverse Colon
  • Larger than the Lesser Omentum
  • Contains Multiple Ligaments:
    • Gastrophrenic Ligament – Stomach to Left Diaphragm
    • Gastrocolic Ligament – Stomach to Transverse Colon
    • Gastrosplenic Ligament – Stomach to Spleen
  • Blood Supply: Right and Left Gastroepiploic Arteries
    • Considered to Have a Rich Vascular Supply

Functions

  • Immune-Regulation:
    • Adheres to Sites of Inflammation and Expands to Contain Intraperitoneal Infection
    • “Milky Spots” Within the Omentum Contain Resident Macrophages to Allow Rapid Migration to Sites of Inflammation for Bacterial Clearance
  • Tissue Regeneration:
    • Omentum Promotes Wound Healing with Tissue Regeneration
    • Promotes Neovascularization/Neoangiogenesis in Adjacent Structures
    • Biological Mechanism is Poorly Understood
  • Contains Double the Normal Concentration of Tissue Factor – Promotes Extrinsic Coagulation and Wound Isolation in Trauma/Infection

Omental Transposition/Flap Over an Injured Organ/Tissue Can Be Used to Promote Healing (Graham Patch)

Greater Omentum

Mesentery

Mesentery: A Double Fold of Visceral Peritoneum Extending from the Posterior Abdominal Wall to the Intestine

The Mesentery is a Single Structure (An Internal Organ) Extending from the Duodenojejunal Flexure to the Distal Mesorectum – Not Separate Sections with Separate Insertions

Structures

  • Mesentery Proper – Mesentery to the Small Intestine (Jejunum/Ileum)
    • “Root of the Mesentery” – The Point Where the Mesentery Proper Attaches to the Posterior Wall
  • Transverse Mesocolon – Mesentery to the Transverse Colon
  • Sigmoid Mesocolon – Mesentery to the Sigmoid Colon
  • Mesoappendix – Mesentery Extending from the Distal Mesentery Proper to the Appendix
  • Mesorectum – Mesentery to the Upper Third of the Rectum

Functions

  • Anchors Abdominal Organs to the Posterior Abdominal Wall
  • Contains the Blood Vessels (SMA, IMA, Portal System) and Nerves that Supply the Intestine
  • Numerous Lymphatic Vessels and Lymph Nodes
  • Stores Fat

Mesentery Proper 1

Retroperitoneum

Retroperitoneum: The Anatomical Space Behind the Peritoneum

Retroperitoneal Organs Have Peritoneum Only on the Anterior Surface and are Not Suspended by Mesentery

Retroperitoneal Structures

  • GI Tract
    • Esophagus
    • Duodenum – Not the First Part
    • Colon (Ascending and Descending) – Not the Transverse or Sigmoid
    • Rectum
  • Aorta and Inferior Vena Cava (IVC)
  • Pancreas – Not the Tail
  • Kidneys
  • Ureters
  • Suprarenal/Adrenal Gland
  • MNEMONIC: “SAD PUCKER” (Suprarenal, Aorta/IVC, Duodenum, Pancreas, Ureters, Colon, Kidneys, Esophagus, Rectum)

Origin

  • Primary Retroperitoneal: Structures Retroperitoneal Throughout Development
    • Esophagus
    • Rectum
    • Aorta and Inferior Vena Cava (IVC)
    • Kidneys
    • Ureters
    • Suprarenal/Adrenal Gland
  • Secondary Retroperitoneal: Structures Were Initially Intraperitoneal and Suspended by Mesentery by Migrated Retroperitoneal During Development
    • Duodenum – Not the First Part
    • Colon (Ascending and Descending) – Not the Transverse or Sigmoid
    • Pancreas – Not the Tail

Retroperitoneum – Viewed from Behind

References

  1. https://www.scientificanimations.com/wiki-images (License: CC BY-SA-4.0)