Pancreatic secretion contains enzymes (Table 12.2) for digesting all three major food component: carbohydrate, protein and fats.

 

(e)Intestinal glands: These are formed by modification of surface epithelium of small intestine. The two main intestinal glands are Brunner’s gland and Crypts of Lieberkühn.

(i)Brunner’s glands are found only in first few centimetres of duodenum. They secrete large amount of alkaline mucus to protect the duodenal wall from highly acidic gastric juice and to neutralize hydrochloric acid.

(ii)Crypt of Lieberkühns are small pits located all over the entire surface of the small intestine, lies between the intestinal villi. They are covered by epithelium composed of two types of cells. 1) Goblet cells: secrete mucus. 2) Enterocytes: secrete water and electrolyte, also reabsorb the water and electrolyte along with the end product of digestion over the surface of adjacent villi. At the base of these crypts, paneth cells and argentaffin cells are present.

Paneth cells found mainly in duodenum are rich in zinc and contain acidophilic granules. Argentaffin cells synthesize secretin hormone and 5-hydroxytryptamine.