COMLEX USA Comprehensive Osteopathic Medical Licensing Examination Practice 2026 - Free COMLEX Practice Questions and Study Guide

The descending colon, sigmoid colon, and rectum are primarily innervated by segments of the spinal cord that correspond to the lower lumbar and sacral levels. The correct range for the descending colon and sigmoid colon is indeed from L1 to L2.

More specifically, the descending colon begins at the level of the left colic flexure (splenic flexure), where it continues downward along the left side of the abdominal cavity to the sigmoid colon. The sigmoid colon, which is S-shaped and leads into the rectum, is located in the pelvic cavity and is primarily associated with the lower lumbar and sacral levels.

The rectum extends from the sacral region (specifically S3) and continues down to the anal canal. Therefore, understanding the innervation and anatomical relationships of these structures is crucial because it aids in comprehending referred pain patterns and surgical approaches in the lower abdomen and pelvis. Moreover, the chosen vertebral levels of L1 to L2 coincide with the origins of relevant autonomic nerves that supply these parts of the colon, emphasizing the connection between certain vertebral levels and gastrointestinal functions.