This document provides an overview of the peritoneum and peritoneal cavity through a lecture with various references and links. It discusses the reflections of the peritoneum in the male and female abdomen and the supracolic and infracolic compartments. It also details the epiploic foramen/omental foramen/foramen of Winslow, which is the vertical slit-like opening that allows communication between the lesser and greater sacs. Finally, it describes the lesser sac or omental bursa, the large recess behind the stomach with a "hot water bag" shape that is closed off except where it connects to the greater sac through the epiploic foramen.