Digestive Functions of the Large Intestine

The final stages of digestion occur in the large intestine when the cecum receives chyme, which has little nutritional value except for the indigestible carbohydrates.

Over the next 12 to 24 hours, these carbohydrates are fermented by the gut bacteria to produce energy and synthesize essential vitamins.

As the chyme moves into the colon, it triggers two characteristic sluggish contractions — haustral churning and mass peristalsis.

Haustral churning involves the rhythmic contraction and relaxation of smooth muscles in individual haustra.

In the ascending and transverse colon, as the chyme distends a haustrum to capacity, the walls contract and squeeze the contents into the next haustrum.

These segmented minute-long movements occur every 30 minutes to allow mixing and absorption of vitamins, water, and electrolytes, such as sodium and chloride.

Additionally, peristalsis at a slower rate of 3–12 contractions per minute assists haustral churning.

Lastly, strong wave-like contractions around the middle of the transverse colon, called mass peristalsis, push residual contents over large areas 3 or 4 times daily toward the rectum.