Anatomy and Physiology of the Colon and Rectum

Abstract

The colon is divided into sections that include the cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid, and rectum. While there is universal agreement about the major sections of the colon, the nomenclature of the lower portion of the large bowel has been a subject of some disagreement. Gilchrist’s designation will be used in this book. He divides the rectum into two portions. The lowermost is the extraperitoneal rectum that lies entirely below the peritoneal floor and averages about 8 cm in length. The upper portion of the rectum is the intraperitoneal rectum; it is also about 8 cm in length and extends upward to the sigmoid, which is marked by the transition to a definite mesentery. In this method of nomenclature the old designation “recto-sigmoid” is eliminated and replaced by the term “intraperitoneal rectum.”