Illustration of the detail of the anatomy of the caecum showing two orifices. The larger is the ileocaecal valve that restricts reflux into the ileum when the caecum is loaded with faecal material. The smaller orifice is continuous with the appendix. The colonic mucosal surface is formed into ridges and folds. From Lizars, J. 1823 A system of anatomical plates of the human body. W.H. Lizars, Edinburgh.