Peritoneal cavity

General characteristics and layers

The peritoneum is a thin serous membrane that performs essential barrier and fixation functions. Anatomically, it consists of two continuous, seamlessly transitioning layers:

1. Parietal peritoneum (peritoneum parietale) — the lining layer that covers the walls of the abdominal cavity from the inside.
2. Visceral peritoneum (peritoneum viscerale) — the investing layer that directly covers the organs themselves, forming their outer serous coat.

The space between these layers is called the peritoneal cavity (cavum peritonei). Normally, this is not an open void, but a narrow capillary slit. The pressure within it ranges from 0 to 0.25 mm Hg, which is practically equal to atmospheric pressure.

The physiological volume of serous fluid is only 25–30 ml. However, during pathological processes (inflammation, trauma), the cavity can expand significantly, accommodating vast amounts of exudate, pus, or spilled blood.

Organ relations to the peritoneum

Depending on the surface area of the organ covered by the visceral layer, operative surgery and topographic anatomy distinguish three types of peritoneal arrangement:

• Intraperitoneal — the organ is covered by the serous membrane on almost all sides (e.g., stomach — ventriculus, jejunum — jejunum, ileum — ileum, transverse colon — colon transversum).
• Mesoperitoneal — the organ is covered by the peritoneum on three sides, while one side lacks a serous covering (e.g., liver — hepar, ascending and descending colons).
• Extraperitoneal (including retroperitoneal) — the organ is covered by the peritoneum on only one side (e.g., pancreas — pancreas, duodenum — duodenum, rectum — rectum).

Topographic classification strictly divides these structures: intra- and mesoperitoneally located structures belong to abdominal organs, whereas extraperitoneal (retroperitoneal) structures form retroperitoneal organs (spatium retroperitoneale).

Division of the abdominal cavity into compartments

To facilitate the study of complex topography and pathways of infection spread, the abdominal cavity is divided into two compartments (upper and lower).

The natural anatomical boundary between them is the transverse colon (colon transversum) and its mesentery (mesocolon transversum). Everything above this line belongs to the upper compartment, and below it to the lower compartment.

Topography on a median sagittal section

By studying the course of the peritoneum on a sagittal section (in males), one can trace the formation of the ligamentous apparatus and specific recesses:

• In the upper compartment, the peritoneum, passing from the diaphragm (diaphragma) to the liver, forms the coronary ligament (lig. coronarium hepatis). The hepatogastric ligament (lig. hepatogastricum) descends from the liver to the stomach.
• Behind the stomach, an isolated slit-like space is formed — the omental bursa (bursa omentalis). Access to it is through the omental foramen (foramen epiploicum).
• A massive folded apron — the greater omentum (omentum majus) — hangs down from the greater curvature of the stomach.
• In the lower compartment, we see the root of the mesentery of the small intestine (radix mesenterii), loops of the jejunum and ileum, and the sigmoid mesocolon (mesocolon sigmoideum).
• Descending into the pelvic cavity in males, the peritoneum passes from the rectum (rectum) to the urinary bladder (vesica urinaria), forming a deep rectovesical pouch (excavatio rectovesicalis).

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Boundaries and walls of the omental bursa (bursa omentalis)
• Topography of the omental foramen (foramen epiploicum)
• Course of the peritoneum in the lesser pelvis
• Ligamentous apparatus of the liver and stomach
• Anatomy of the greater omentum (omentum majus)

Other topics in the section "Topographic Anatomy of the Abdomen"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.