ovarian bursa Ovaries of some animals are surrounded by a thin membranous sac, the bursa, and are isolated from the peritoneal cavity. The bursa is continuous with the orifice of the oviduct. The bursa is not continuous in other mammals (eg., farm animals and human beings); ovaries of these species can be exposed within the abdomen, and thus ectopic pregnancy is possible[http://www.uwyo.edu/wjm/repro/femanat.htm] fold of peritoneum