20.5: Large Intestine

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The large intestine runs from the appendix to the anus. It frames the small intestine on three sides. Despite its being about one-half as long as the small intestine, it is called large because it is more than twice the diameter of the small intestine, about 3 inches.

This image shows the large intestine; the major parts of the large intestine are labeled. — Figure \(\PageIndex{1}\): Large Intestine The large intestine includes the cecum, colon, and rectum. (CC-BY-4.0, OpenStax, Human Anatomy)

Three features are unique to the large intestine: teniae coli, haustra, and epiploic appendages (Figure \(\PageIndex{2}\)).

This image shows the Taenia Coli, haustra and epiploic appendages, which are parts of the large intestine. — Figure \(\PageIndex{2}\): Teniae Coli, Haustra, and Epiploic Appendages (CC-BY-4.0, OpenStax, Human Anatomy)

Histology

There are several notable differences between the walls of the large and small intestines (Figure \(\PageIndex{3}\)). For example, few enzyme-secreting cells are found in the wall of the large intestine, and there are no circular folds or villi. Other than in the anal canal, the mucosa of the colon is simple columnar epithelium made mostly of enterocytes (absorptive cells) and goblet cells. In addition, the wall of the large intestine has far more intestinal glands, which contain a vast population of enterocytes and goblet cells. These goblet cells secrete mucus that eases the movement of feces and protects the intestine from the effects of the acids and gases produced by enteric bacteria. The enterocytes absorb water and salts as well as vitamins produced by your intestinal bacteria.

This image shows the histological cross section of the large intestine. The left panel shows a small region of the large intestine. The center panel shows a magnified view of this region, highlighting the openings of the intestinal glands. The right panel shows a further magnified view, with the microvilli and goblet cells. — Figure \(\PageIndex{3}\): Histology of the large Intestine (a) The histologies of the large intestine and small intestine (not shown) are adapted for the digestive functions of each organ. (b) This micrograph shows the colon’s simple columnar epithelium and goblet cells. LM x 464. (credit b: Micrograph provided by the Regents of University of Michigan Medical School © 2012) (CC-BY-4.0, OpenStax, Human Anatomy)

* Enteric neuron.