Peritoneum

Introduction

Introduction to the Peritoneum

The peritoneum is a serous membrane that lines the abdominal cavity (parietal layer) and covers the intra‑abdominal organs (visceral layer). It provides a frictionless surface for organ movement, serves as a conduit for blood vessels, lymphatics, and nerves, and contributes to immune surveillance. The peritoneal cavity is a potential space that can expand to accommodate fluid, gas, or pathological collections.

Abdominal Peritoneal Compartments

The peritoneal cavity is divided into the greater sac, which occupies most of the abdomen, and the lesser sac (omental bursa) located posterior to the stomach. Communication between the two occurs via the epiploic foramen (of Winslow). Understanding these compartments is essential for interpreting the spread of infection, fluid, or tumor within the abdomen.

Study

Parietal Peritoneum

The parietal peritoneum lines the abdominal wall, diaphragm, and pelvic floor. It is richly innervated by somatic nerves, making it sensitive to pain, pressure, temperature, and touch. Its blood supply derives from the abdominal wall vessels, and it serves as a scaffold for the attachment of mesenteries and ligaments.

Visceral Peritoneum

The visceral peritoneum covers the external surface of most abdominal organs, forming organ-specific peritoneal layers that blend at mesenteric borders. It is supplied by autonomic fibers, rendering it insensitive to sharp pain but responsive to stretch and chemical irritation. Serous fluid secreted by the visceral layer lubricates organ movement within the cavity.

Omenta

The greater omentum hangs from the greater curvature of the stomach, draping over the intestines, and contains fat, lymphatics, and immune cells that can wall off infection. The lesser omentum connects the lesser curvature of the stomach and the first part of the duodenum to the liver, containing the hepatic artery, portal vein, and bile duct within the hepatoduodenal ligament. Both omenta play roles in fat storage, immune response, and surgical access.

Peritoneal Reflections and Ligaments

Peritoneal reflections form mesenteries that suspend the intestines, such as the transverse mesocolon and mesentery proper, providing a conduit for vessels, nerves, and lymphatics. Ligaments like the falciform, gastrocolic, and hepatogastric ligaments are double‑folded peritoneal sheets that anchor organs to the diaphragm or abdominal wall. These structures delineate peritoneal spaces and guide surgical planes.

Clinical Significance of Peritoneal Spaces

Pathology can accumulate in specific peritoneal compartments; for example, fluid in the lesser sac may indicate pancreatic leakage, while free intraperitoneal air suggests perforated viscus. Peritoneal dialysis utilizes the extensive vascular surface of the peritoneum for solute exchange. Knowledge of peritoneal anatomy is critical for safe laparoscopic entry, drainage procedures, and oncologic staging.

Summary

Key Takeaways

The peritoneum consists of parietal and visceral layers that create a potential space divided into greater and lesser sacs. Omenta and mesenteric reflections provide vascular, lymphatic, and immune pathways while anchoring abdominal organs. Understanding peritoneal compartments guides diagnosis and management of intra‑abdominal disease.

Clinical Correlate

Accurate knowledge of peritoneal anatomy is essential for interpreting peritonitis, planning surgical approaches, and performing peritoneal dialysis. Misplacement of instruments or failure to recognize peritoneal spaces can lead to complications such as organ injury or inadequate drainage.