Final answer:
The word referring to the area behind the peritoneum is "retroperitoneal." This term is used to describe organs or tissues located behind the peritoneal lining of the abdominal cavity, such as the duodenum, pancreas, and parts of the large intestine.
Step-by-step explanation:
The term that means pertaining to behind the peritoneum is retroperitoneal. The peritoneum is a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue, and includes two distinct regions: the visceral peritoneum, which envelops the internal organs, and the parietal peritoneum, which lines the abdominal wall. The space bounded by these two regions is known as the peritoneal cavity. Retroperitoneal structures, such as parts of the intestines, the pancreas, and the kidneys, are located behind the peritoneum, between the parietal peritoneum and the abdominal wall.
During fetal development, certain digestive structures, including the duodenum, pancreas, and parts of the large intestine, remain completely or partially posterior to the peritoneum, classifying them as retroperitoneal. The presence of these organs in this space is crucial as they are often less mobile and can be affected by different diseases compared to intraperitoneal organs. Disorders such as peritonitis, the inflammation of the peritoneum, do not typically affect these retroperitoneal organs directly but can impact surrounding structures.