In the human gastrointestinal tract, most of the digestive system, from the mouth to the anus, follows the general scheme of hollow organs composed of four layers: the inner layer or mucosa epithelium, the submucosa, the muscularis, and the outer protective layer known as the adventitia or serosa. Following the small intestine, the large intestine includes the ascending, transverse, descending, and sigmoid sections of the colon.

Typically, the simple epithelial tissue of the colon is made of up several different types of cells, including the characteristic goblet cells and numerous columnar absorptive cells. Named for their shape that incorporates a narrow cytoplasm base, and mucous resembling the bell of a wine goblet, goblet cells are rich with large Golgi apparatus. Unlike the preceding ileum of the small intestine, the colon does not feature villi, but has gastric pits, as does the stomach. The colon functions as the site of absorption of water, residual amino acids, lipids, carbohydrates, electrolytes, and some vitamins, while it also compacts the feces for elimination. The copious mucus produced by the goblet cells is required to facilitate passage of the dehydrated, undigested matter.

Hormones, such as vasoactive intestinal peptide, increase gut motility and stimulate intestinal ion, water, and mucus secretions, keeping food and undigested waste moving along the gastrointestinal tract. Recently, the genes that control the production and release of vasoactive intestinal protein hormone were located and mapped as part of the Human Genome Project. The bioactive peptide is now being employed in hormone therapies following cardiac surgery, menopause, and in some cancer treatments. Along with the goblet cells and columnar absorptive cells, a few enterocytes and migrating lymphocytes are found in the human colon mucosa epithelium. The crypts of Lieberkuhn, tubular glands of the colon, extend from the surface through the thickness of the mucosa.

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