Atlas of Human Anatomy by Netter

Superior rectum

Primarily retroperitoneal organs

Organs that develop and remain beneath the parietal peritoneum

Only the kidneys

Secondarily retroperitoneal organs

Organs that developed with a short mesentery

Become pushed against parietal peritoneum lining the body wall by growth of other organs, primarily the small intestine.

Mesentery of organ fuses with parietal peritoneum: fusion fascia

Peritoneum covers only its anterior surface, hence, secondarily retroperitoneal

Organ can be freed at its lateral edge, along the plane of the fusion fascia

Include

Adrenal glands

Pancreas

Parts two through four of the duodenum

Ascending and descending colon

Omenta

[Plate 265, Omental Bursa: Cross Section]

Omentum = double-layered fold of peritoneum

Lesser omentum: connects lesser curve of stomach and proximal duodenum to liver

Passes from the stomach and first part of the duodenum to adjacent organs

Consists of two parts:

Hepatogastric ligament

Hepatoduodenal ligament

Greater omentum

Hangs down from the greater curve of the stomach and proximal duodenum

Folds back on itself to attach to the transverse colon

Mesenteries

Mesentery = double layer of peritoneum created by invagination of peritoneum by an organ