The abdominal cavity extends only to the brim of the pelvis; the pelvic cavity is separate. The peritoneal cavity is not synonymous with the abdominal cavity: some of the abdominal organs project comparatively little forward into it and, as in the case of the kidneys, may be only partly covered with the peritoneum. The peritoneal cavity includes the pelvis, so that an infection of the pelvic peritoneum of necessity involves a part of the general peritoneal cavity.

The peritoneum is a closed sac lining the abdomen and pelvis into which the various abdominal and pelvic organs grow. As the organs increase in size they push farther into the abdominal cavity and the peritoneum covers more of their surface, until in some cases the two layers (anterior and posterior) meet; thus the organ is left hanging by its peritoneal pedicle. The peritoneum covering the organs is called the visceral peritoneum, that lining the walls of the abdominal cavity the parietal peritoneum. Those parts of the peritoneum joining the visceral and parietal layers receive various names. Sometimes they are called ligaments, - thus we have the various ligaments of the liver, the coronary, lateral, and suspensory; of the spleen; of the uterus; bladder, etc. Sometimes they are called omenta, - thus we have the greater omentum, the lesser or gastrohepatic omentum and the gastrosplenic omentum. Sometimes they receive the name of mesentery, which is applied to the small intestine, and mesocolon, as applied to the large intestine. From this arrangement it is evident that there is some portion of every abdominal and pelvic organ that is not covered by peritoneum. In some organs, as the small intestines, the uncovered part is very small, being at the attachment of the mesentery. In other organs, as the kidneys, it is very large, embracing all their posterior surface. In operating on the abdominal or pelvic organs these attachments are of importance, as a knowledge of them enables the surgeon - for example, in operating on the kidney for renal calculus - to complete his procedures without wounding the peritoneum or opening the peritoneal cavity. The upper and lower limits of the peritoneum are also important, as it is liable to be wounded in operations on the chest and the organs of the pelvis. A knowledge of the course pursued by the peritoneum over the various organs is of service both in diagnosis and operative procedures.

Fig. 412.   Anteroposterior section, showing the peritoneum.

Fig. 412. - Anteroposterior section, showing the peritoneum.

Viewing the body in an anteroposterior section (Fig. 412), and beginning at the umbilicus, the peritoneum is seen to pass upward on the posterior surface of the anterior abdominal wall until it reaches the under surface of the diaphragm, which it covers, to the upper posterior surface of the liver, where it forms the coronary ligament on the right side and the left lateral ligament on the left. It then covers the upper or parietal surface of the liver and curves around the anterior edge and the under or visceral surface as far as the transverse fissure. Thence it proceeds to the stomach, forming the anterior layer of the lesser or gastrohepatic omentum. After covering the anterior wall of the stomach, it leaves the greater curvature to form the anterior layer of the greater omentum. It next passes to the transverse colon, which it covers and passes back to the spine at the lower border of the pancreas. It then goes downward, covering the transverse portion of the duodenum and forming the anterior layer of the mesentery. Having covered the small intestine, it goes back to the spine, forming the posterior layer of the mesentery, and descends until it reaches the rectum. From the rectum it is reflected forward to the upper part of the vagina and uterus in the female, forming the recto-uterine pouch (or pouch of Douglas) or on the bladder in the male, being at this point about 7.5 cm. (3 in.) distant from the anus. After covering the fundus and body of the uterus, it is reflected at the level of the internal os to the bladder, forming the uterovesical fold. From the top of the bladder it passes up the abdominal wall to reach the umbilicus.

The peritoneum lining the lesser cavity can be followed upward from the anterior surface to the pancreas. It ascends on the posterior abdominal wall to the under surface of the liver, forming the under layer of the coronary and left lateral ligaments, and at the transverse fissure is reflected to the posterior surface of the stomach, forming in its course the posterior layer of the gastrohepatic omentum. From the greater curvature it passes downward and then upward to the colon, forming the posterior layer of the greater omentum. From the posterior edge of the transverse colon it passes to the anterior surface of the pancreas, having in its course formed the upper (cephalad) layer of the transverse mesocolon.

Fig. 413.   Transverse section made through the foramen of Winslow. (Viewed from above).

Fig. 413. - Transverse section made through the foramen of Winslow. (Viewed from above).