Human digestive system in the small intestine. Water and minerals are reabsorbed back into the blood in the colon of the large intestine, where the environment is slightly acidic. Some vitamins, such as biotin and vitamin K produced by bacteria in the gut flora of the colon are also absorbed. The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B12. Vitamin B12 (cobalamin), is carried to, and through the stomach, bound to a glycoprotein secreted by the salivary glands - transcobalamin I also called haptocorrin, which protects the acid-sensitive
Digestive enzyme system) activates the ENS, in turn leading to the release of acetylcholine. Once present, acetylcholine activates G cells and parietal cells. Pancreas is both an endocrine and an exocrine gland, in that it functions to produce endocrinic hormones released into the circulatory system (such as insulin, and glucagon), to control glucose metabolism, and also to secrete digestive/exocrinic pancreatic juice, which is secreted eventually via the pancreatic duct into duodenum. Digestive or exocrine function of pancreas is as significant to the maintenance of health as its endocrine function. Two of the population of cells in the pancreatic parenchyma make up its