Colon: anatomy and structural anomalies

In addition to understanding the gross anatomy of the colon and rectum, detailed knowledge of their histological features and cellular components are critical in the appreciation of physiological and pathological processes of the large bowel. The colon and rectum are considered as a single organ. However, it is prudent to subdivide the colon and rectum for the purposes of anatomical discussion because there are considerable differences between the two in their anatomical features, structural relationships, and physiological aspects. Throughout its course, the colon has variable degrees of fixation to the retroperitoneum, as a reflection of its embryological development. Blood is supplied to the colonic wall by the vasa recta, which traverse the muscularis propria layer to provide blood supply to the mucosa and submucosa. The lymphatics drain via the corresponding arterial supply. Pathological evaluation of lymph nodes for the presence or absence of metastases is critical in the staging of colorectal cancers.