Understanding colonic symptoms: Constipation, diarrhea, and fecal incontinence

The colon is a large hollow organ that is derived embryologically from the primitive mid and hindguts. Like the other gastrointestinal hollow organs, the colon has both circular and longitudinal smooth muscle layers which are innervated by the autonomic nervous system and enteric neurons but uniquely, the longitudinal muscle of the colon is separated into three bundles known as taenia coli. The configuration of the taenia causes the colon to be divided into haustral folds which help to slow the passage of fecal material and facilitate absorption to subserve its important function of storage. The main mechanism for propulsion of stool in the colon is by mass movements which occur several times each day (but never during sleep) and often may lead to defecation. They are characterized radiologically by proximal contraction of the bowel wall coupled with inhibition of distal haustral segments. The manometric correlates of this phenomenon are known as high-amplitude propagated contractions (HAPCs).