In all examined species the small intestine (SI) consisted of a long and convoluted tube with a constant diameter
throughout its length. The first intestinal loop originates from the pyloric sphincter, as a region that curves upward from left to right. Then, it descends slightly, becoming an entangled organ located medially in the coelomic cavity. The first shorter region, soon after the pyloric sphincter, was considered the duodenum; and the longer and more coiled region was considered the jejunum/ileum, because the transition between the jejunum and ileum could not be determined. In C. mydas, L. olivacea, C. caretta and E. imbricata mucosa of the duodenum was characterized by the presence of reticular folds. The jejunum/ ileum region had rectilinear longitudinal folds (Fig. 12). However in D. coriacea the small intestine had reticular folds in a pattern similar to a “honey-combed” throughout its length (Fig. 11), and it was not possible to identify the limits of each region of the small intestine.