< Peritoneum and Peritoneal Reflections

Peritoneum and Peritoneal Reflections

The best way to try to visualize the peritoneum and its reflections is to examine sagittal and cross sections through the abdomen. After looking at images of these sections, students who have a cadaver available can then follow the road map that I will be giving as a way to classify various organs in the abdominal cavity before actually displaying them.

First, we will take a look at a sagittal section through the abdomen just to the right of the midline of the body. The parietal peritoneum is colored bright blue and the visceral peritoneum is colored magenta.

After cutting through the abdominal wall, if you put your hand under the wall, you will be touching parietal peritoneum. If you start by putting your finger as high as possible 1, then run it along the inner aspect of the abdominal wall 2 until you reflect onto the superior surface of the urinary bladder 3, then over the uterus in the female 4, then down into the pouch of Douglas 5, again in the female, up along the anterior surface of the rectum onto the posterior abdominal wall 6 until you reach the root of the mesentery of the small intestine. From here you follow the mesentery of the small intestine 7 going around its coils until you reach the other side of the mesentery back down to the posterior abdominal wall where you will cross over the horizontal part of the duodenum 8. Your finger will then travel along the inferior aspect of the gastrocolic ligament 9, down the posterior surface of the greater omentum (go) to its lower border and back up along its anterior surface 11. Your finger then passes over the anterior surface of the stomach 12, along the anterior lamina of the lesser omentum 13. At this time you probably couldn't continue the trip because you would have to enter the epiploic foramen (ef) to enter the lesser peritoneal cavity (lpc) where visceral peritoneum lines this space anteriorly and parietal peritoneum posteriorly.

Second, we will take a look at a couple of cross sections taken through the abdomen: 1)one through the level of the liver, stomach and spleen and 2)another through a lower level. These levels are shown at A and B on the sagittal section above.

Again, start at 1 and follow around the peritoneal cavity. Once on the back of the abdomen, 2 you will reflect onto the anterior surface of the right kidney, pass through the epiploic foramen, along the posterior wall of the lesser peritoneal cavity, 3 then up along the renal lienal ligament 4 onto the posterior surface of the stomach 5. Your finger will continue through the epiploic foramen again to turn around the free margin of the lesser omentum 6, then over the anterior surface of the stomach again 7. Continue to follow around the greater curvature of the stomach 8 until you reflect again along the gastrolienal ligament 9. Your finger will now pass around the spleen, onto the left kidney to the parietal peritoneum and back to the falciform ligament fl.

In the second cross section, start out anteriorly in the abdomen 1. Trace around to the posterior abdominal wall until you reach the lateral paracolic gutter 2, over the anterior surface of the ascending colon ac, down into the medial paracolic gutter 3then onto the large vesselsvessels posterior abdomen. Over the front of the vessels, your finger will travel along the right part of the mesentery of the small intestine 4. You then travel around the coils of the small intestine until you reach the posterior abdominal wall again 5. Continue along the left side, over the descending colon dc and finally, up to the anterior part of the abdominal wall.

In the above discussion, you followed the peritoneal lining of the abdominal cavity in two different directions and classified organs and specialities of the periperitoneum along the way. The peritoneal cavity is a closed cavity made up of a thin, one-cell-thick serous membrane. The word serous denotes that this membrane can produce fluid;slidinghe intestinal tract is highly moveable within the abdominal cavity, there is a need to have some lubrication between the sliding surfaces and this is produced by the peritoneum. On the other hand infections and other pathologies might result in an overproduction of fluid, which is not what one would like. There are certain pathological conditions that produce extra fluid in the peritoneal cavity and this results in what is called ascites.

The peritoneum has the following properties:
  1. it becomes double in certain areas. This double layer of peritoneum is given different names: mesentery, ligament, fold, or omentum.
  2. as already mentioned, it lines the abdominal cavity
  3. it almost completely surrounds some parts of the intestinal tract. These parts are called intraperitoneal structures.
  4. it only covers the anterior part of some structures. These structures are called retroperitoneal. Retroperitoneal structures include: urinary system, ascending colon, descending colon, horizontal part of duodenum, pancreas (except for its tail).
  5. it produces a covering around some of the intestines. The covering is called its serous coat.
  6. peritoneal folds are usually caused by underlying blood vessels, ducts or embryonic remnants.
Inguinal Region   Abdominal Cavity

cadaver This is copyrighted©1999 by Wesley Norman, PhD, DSc