Final answer:
The peritoneum's modifications include the greater omentum, an apron-like fold over the intestines; the peritoneal cavity, a lubricated potential space; and the mesentery, connecting intestines to the body wall.
Step-by-step explanation:
The peritoneum is a broad serous membranous sac that plays a crucial role in holding the abdominal organs in place and consists of the visceral peritoneum and the parietal peritoneum. The visceral peritoneum includes multiple large folds that envelope abdominal organs, which contain blood vessels, lymphatic vessels, and nerves. These folds are modifications of the peritoneum that help support and supply the organs they cover.
The five major peritoneal folds, which can be considered as modifications, include the following:
- An apron-like structure that lies superficial to the small intestine and transverse colon
- The greater omentum, which is a large fold draping over the intestines and is a site of fat deposition for some people
- The mesentery, a fold that attaches the intestines to the posterior abdominal wall, providing stability and passage for blood vessels and nerves
The peritoneal cavity is the potential space between these peritoneal surfaces, containing a small amount of fluid acting as a lubricant. Some organs, such as the duodenum, pancreas, and certain parts of the large intestine (ascending and descending colon, and the rectum), are retroperitoneal, meaning they are located behind the peritoneum during fetal development and hence are only partially covered or not covered at all by the peritoneum.