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THE PERITONEUM

BIG PICTURE

The abdominopelvic cavity is lined with a serous membrane called the peritoneum. The peritoneum completely or partially lines the internal surface of the abdominal wall and organs of the abdominal cavity. Like other serous sacs and their associated organs, the peritoneal sac and its organs have the basic structural relationship of a “fist in a balloon.” This analogy accurately portrays the relationship of the peritoneal organs and the peritoneum. Digestive organs represent the “fist” and the peritoneal sac represents the “balloon.”

PERITONEAL SAC

The peritoneal sac is composed of a serous membrane that lines the internal surface of the abdominal cavity and consists of the following parts (Figure 8-1A–C):

  • Parietal peritoneum. The portion of the serous sac in contact with the internal surface of the abdominal wall, diaphragm, and pelvis. The posterior surface of the parietal peritoneum forms the anterior wall of the retroperitoneal space, which contains the kidneys, ureters, adrenal glands, aorta, IVC, and other structures.

  • Visceral peritoneum. The serous membrane that surrounds the parts of the gut tube and forms the outer layer of the organs. The visceral peritoneum is also referred to as the tunica serosa.

  • The mesentery. The parietal peritoneum reflects off of the posterior abdominal wall, forming a fused, double layer of peritoneum surrounding the blood vessels, nerves, and lymphatics to abdominal organs. This double layer of peritoneum, known as the mesentery, suspends much of the small intestines from the posterior abdominal wall.

  • Peritoneal fluid. Peritoneal membranes secrete a serous fluid that lubricates the peritoneal surfaces, enabling the intraperitoneal organs to glide across one another with minimal friction.

  • Peritoneal cavity. The peritoneal cavity is the fluid-filled space within the peritoneal sac. The peritoneal cavity is completely closed in males. In females, the peritoneal cavity has two tiny openings into the ostium of the uterine tubes, which provides a possible communication with the outside via the uterus and vagina. The peritoneal cavity is subdivided into the greater and lesser sacs:

    • Lesser sac (omental bursa). The space deep to the stomach and lesser omentum.

    • Greater sac. The remaining part of the peritoneal cavity. The greater and lesser sacs communicate with each other through the epiploic foramen (of Winslow) formed by the right border of the hepatoduodenal ligament.

Figure 8-1:

A. Parasagittal section of the abdomen showing the peritoneum. B. Relationship of the mesentery and neurovascular supply to the intraperitoneal organs. C. Cross-section of the peritoneum and mesentery at approximately the T11 vertebral level.

OMENTUM

The omentum refers to modified mesenteries associated with the stomach and liver (Figure 8-1A).

  • Greater omentum. An apron-like fold of peritoneum that develops from the dorsal mesentery and attaches between the transverse colon and greater curvature of the stomach.

    • Quadruple layer of ...

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