PER'ITONE'UM ( Lat. peritoneu m , per i to from Gk. 7repLr6vatov, ritonoion, neu.
of rfinr6vatos; prritonaios, stretched around, from reptretvelv, periteimin. to stretch around, from /rept, prri, around .7-chap, (chitin, to stretch).
A -.emus membrane nt Bich more or less com pletely invests all the viscera lying in the abdomi nal and pelvic cavities. and is then reflected upon the walls of the abdomen, so that there is a visceral and a parietal layer. Numer ous folds are formed by the visceral layer as it passes from one organ to another. They serve to hold the parts in position. and at the same time inclose vessels and nerves. Some of these folds are termed ligaments, from their serving to sup port the organs. Thus we have ligaments of the liver, spleen, bladder, and uterus formed by peri toneal folds. Others are termed mesenteries, and connect the intestines with the vertebral column. They are the mesentery proper (q.v.), which has been already described, the ascending, transverse, and descending meso-colon, and the meso-rectum. Lastly, there are folds called 0tnento, which pro ceed from one viscus to another. They are three in number—viz. the lesser or gastro-hepatic
omentum, which extends front the under surface of the liver to the lesser curvature of the stom ach; the gastro-splenie omentum; and the great (or gastro-colic) omentum, which consists of four layers of peritoneum, the two which descend from the stomach, and the same two returning upon themselves, and ascending as high as the trans verse colon, where they separate, and inclose that organ. These separate layers may lie easily seen in the young subject. but in the adult they are more or less blended. The great omentum always con tains some adipose tissue, which in corpulent persons often accumulates to an enormous ex tent. Its use appears to be (1) to protect the in testines from cold and from injury by covering them anteriorly as with an apron, and (2) to facilitate their movement upon each other during their vermicular action. In the female the peri toneal cavity is not completely closed, as the Fallopian tubes open into it by their free ex tremities. Inflammation of the peritoneum is termed peritonitis (q.v.).