2 Normal Motility and Smooth Muscle Function

The gastrointestinal tract normally functions to move ingested food, in an organized fashion, from the oropharynx, through the stomach, small intestine and colon and into the rectum, from which it can be expelled. The primary function of the colon is to absorb water and electrolytes from the chyme delivered and, thus, determine the frequency, consistency, and volume of stools eliminated. The colon (i) mixes luminal contents so that they are optimally exposed to the absorptive mucosal surface; (ii) slowly propels feces caudally to allow adequate time for the absorption of water, electrolytes, and metabolic products of bacterial degradation; (iii) allows storage of feces; and (iv) rapidly and efficiently propels feces during defecation. Transit time through the colon is significantly slower than through the proximal bowel and is achieved through contractions that are less coordinated. The discoordination is due to highly variable frequency and phase unlocking of electrical activity within the colon. 2 Normal Motility and Smooth Muscle Function