Anatomy and Embryology of the Colon, Rectum, and Anus

Abstract

Although much of our fundamental understanding of the anatomy of the colon, rectum, and anus comes from the efforts of researchers of the 19th and early 20th centuries, comprehensive observations of this region had been made as early as 1543 by Andreas Vesalius through anatomic dissections. However, anatomy of this region, especially that of the rectum and anal canal, is so intrinsically related to its physiology that much can be appreciated only in the living. Thus, it is a region in which the surgeon has an advantage over the anatomist through in vivo dissection, physiologic investigation, and endoscopic examination. However, anatomy of the pelvis is also challenging to the surgeon: the pelvis is a narrow space, packed with intestinal, urologic, gynecologic, vascular, and neural structures, all confined within a rigid and deep osseous-muscular cage. Therefore, detailed anatomy of this region is difficult to learn in the setting of an operating room and it demands not only observations in vivo, but historical reviews, anatomy laboratory studies, including dissections of humans and animals, with in-depth descriptions and drawings and sometimes associated with physiologic evaluation. Based on these studies, some controversial concepts of the anatomy, especially of the rectum and anal canal, have been actually changed. In addition, virtual reality models have been designed to improve visualization of threedimensional structures and more properly teach anatomy, pathology, and surgery of the anorectum and pelvic floor.