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Cells of the Small and Large Intestines Small Intestine Exocrine Function The small intestine is primarily composed of simple columnar epithelial cells with microvilli facing the lumen for absorption of digested material. Intestinal crypts (also called the crypts of Lieberkühn) are analogous to gastric glands of the stomach and are formed by invaginations of the epithelium. Within the crypts are paneth cells, which secrete multiple defensive proteins including lysozyme definsins and phospholipase to protect the small intestine from pathogens which have survived the stomach compartment. There are also Goblet cells, which secrete mucous for protection from the acids of the stomach and enzymes from accessory organs. Small Intestine Endocrine Function The small intestine also has enteroendocrine cells which secrete hormones for regulation of absorption of nutrients. S cells produce secretin to buffer intestinal pH. I cells (also called CCK cells) secretecholecystokinin, which stimulates the release of digestive enzymes from the pancreas and gall bladder in to the intestine. K cells secrete gastric inhibitory peptide (GIP; also called glucose-‐dependent insulinotropic peptide), which influences insulin levels Cell Type Location in the Mucosa Function Columnar epithelium with microvilli Lining Digestion and absorption of nutrients in chyme Goblet Intestinal crypts Secretion of mucous Paneth Intestinal crypts Secretion of the bactericidal enzyme lysozyme and other defensive proteins; phagocytosis Enteroendo crine S cells Intestinal glands Secretion of the hormone secretin I (or CCK) cells Intestinal glands Secretion of the hormone cholecystoki nin K cells Intestinal glands Secretion of the hormone gastric inhibitory peptide (GIP) Large Intestine Exocrine Function Most of the mucosa of the large intestine is composed of simple columnar epithelial cells. An exception is the distal anal canal, which is composed of nonkeratinized stratified squamous epithelial cells. The stratified epithelium is more durable to the abrasion that occurs when feces moves. The large intestine also has crypts, which contain both epithelial cells and goblet cells. Since most digestion and absorption occurs before the large intestine, the only significant secretion is mucus, which lubricates the passage of digestive residue.