Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

Which spinal level is commonly associated with the colon?

1. T10-T12

2. T12

3. L1-L2

4. T8-T10

The correct answer is: T10-T12

The spinal levels that are commonly associated with the colon are T10-T12 due to the innervation provided by the sympathetic nervous system. The colon receives autonomic innervation primarily from the pelvic splanchnic nerves, which arise from the sacral region; however, the general visceral afferents and sympathetic fibers arise from the thoracic levels, particularly from T10 to T12. These levels correspond to the areas in the spinal cord where presynaptic sympathetic neurons for the colon originate and project to the celiac and superior mesenteric ganglia. The vagus nerve primarily innervates the proximal portion of the colon, while the distal part is innervated by sacral nerves (S2-S4) via parasympathetic pathways. However, the sympathetic innervation primarily involves the thoracic and upper lumbar segments reaching up to T12, which is critical for regulating colonic motility and secretions. Other options refer to spinal segments that either do not have relevant innervation or are too specific to be the main contributors for colonic function. Specifically, T12 is too limited as it does not encompass the full range of sympathetic innervation necessary for the entire colon. Similarly, L1-L2 and T8-T10