The peritoneal cavity is a continuous and migratory area between the visceral peritoneum and the parietal peritoneum, forming an irregular, irreversible cavity called the peritoneal cavity (peritoneal cavity). The peritoneal cavity is the largest duct in the body.

The cavity formed by the peritoneum is called the peritoneal cavity, which is divided into the abdominal (upper part) and pelvic (lower part) sections. The male peritoneal cavity does not communicate with the outside; the female peritoneal cavity can communicate with the outside through both fallopian tubes, uterine body, and vagina, so women are more prone to peritoneal cavity infections.

The retroperitoneum is rich in blood vessels and has the functions of absorption and exudation. The retroperitoneum’s ability to absorb abdominal fluids and endotoxins is strongest in the upper abdomen and weakest in the pelvis. Therefore, when there is an infection in the peritoneal cavity, a semi-recumbent position is often adopted to allow the pus to accumulate in the pelvis, thereby reducing the absorption of endotoxins and alleviating the symptoms of peritonitis. When there is inflammation in the peritoneal cavity (such as tuberculous peritonitis), a large amount of fluid exudes outside the peritoneum, known as ascites.

The retroperitoneal and intraperitoneal serous membranes contain many macrophages, which have a defensive function. Under normal circumstances, there is 75-100ml of pale yellow serous fluid in the abdominal cavity, which serves as a lubricant.

The peritoneal cavity is divided into two cavities: the greater peritoneal cavity and the lesser peritoneal cavity. The lesser peritoneal cavity, also known as the omental bursa, is a cavity located behind the lesser omentum and the posterior wall of the stomach; the greater peritoneal cavity is the space outside the omental bursa, also known as the retroperitoneal great bursa. Both communicate with each other through the epiploic foramen (also known as Winslow’s hole).

The peritoneal cavity is demarcated by the transverse colon and mesentery, dividing into the upper and lower sigmoid colon areas. The former is located between the diaphragm, transverse colon, and mesentery, also known as the subdiaphragmatic space, which is divided into upper and lower spaces by the liver. The latter is located below a part of the transverse colon and mesentery.