Large Intestine

About the Large Intestine

The large intestine colon is approximately 1.5 meters long and includes the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The appendix is attached to the cecum. The colon absorbs approximately 1.5 liters of water daily from indigestible food residue, converting liquid chyme into solid feces. It harbors the densest part of the gut microbiome, tens of trillions of bacteria, a number now estimated to be roughly comparable to the number of human cells in the body. These bacteria ferment dietary fiber into short chain fatty acids butyrate, propionate, acetate, which nourish colonocytes and have systemic anti inflammatory effects. Gut bacteria also produce vitamin K, biotin, and folate. Haustra are sacculations giving the colon its segmented appearance. The colon has taeniae coli three longitudinal muscle bands and epiploic appendages fat filled pouches. Mass movements 3 to 4 times daily, particularly after meals gastrocolic reflex, propel contents toward the rectum. Defecation involves relaxation of the internal anal sphincter smooth muscle, involuntary and contraction of the external anal sphincter skeletal muscle, voluntary.