A Bowel Case in Anatomy

In practice

The surgeon plans to remove a diseased segment of the sigmoid colon and join the remaining ends. Start with the path of the bowel. The large intestine runs from the cecum, where the appendix is attached, through the ascending, transverse and descending colon, to the sigmoid colon, then the rectum. The sigmoid lies low on the patient's left. Next, the wall. Like the rest of the canal, the colon has four layers, mucosa, submucosa, muscularis and serosa, and joining two ends of bowel means bringing those layers together securely. Next, the blood supply. A vessel named for a region supplies it, and the distal large intestine, including the sigmoid colon, is drained by the inferior mesenteric vein and supplied by its matching artery, a branch of the abdominal aorta. Controlling those vessels is a key step. Next, the coverings. The peritoneum covers the bowel, and its folds carry the vessels the surgeon must control, while the greater omentum may lie over the area like an apron and need to be moved aside. Finally, what this means at the field: opening the colon brings its bacteria into the field, so the team plans how instruments that touch the bowel will be kept apart from those used for closure; the specimen goes to pathology; and bowel and vascular instruments are needed together.