The oviduct is made up of several segments, including the infundibulum, which contains fimbriae and is located near the ovary, the ampulla, the isthmus, and the pars interstitialis. The first two of these regions have a distinct appearance dominated by an elaborate mucosa thrown into numerous branched folds and surrounded by a relatively thin layer of smooth muscle. These folds become smaller as the tube moves away from the ovary and toward the uterus, and the smooth muscle takes over.