Pancreas lies ventral to the stomach and has both endocrime and exocrime function. Exocrime cells in the pancreas secrete digestive enzymes into pancreatic duct, which merges with hepatic duct from the liver to form common bile duct that enters the duodenum.
Pancreatic enzymes complete the digestion of carbohydrates and proteins and initiate the digestion of lipids.
Trypsin carboxypeptidaze and chymotrypsin digest protein into smaller peptide and amino acids. Lipases convert triglycerides into smaller glycerol and free fatty acids. Amylase converts polysaccharides into disaccharides and monosaccharides. The pancreas also secretes bicarbonate (HCO-3) ions that help neutralize the acidic food residue coming from the stomach. Bicarbonate raises the pH from 2 to 7 for pancreatic enzymes to work.
Role of liver in digestion:
Liver: The largest organ in mammalian body is just under the diaphragm. In the liver millions of specialized cells called hepatocytes take up nutrients absorbed from the intestines and release them into bloodstream. Hepatocytes also manufacture blood protein prothrombin and albumin. Liver removes amino acids from organic compounds. Liver forms urea from proteins and conversion of excess amino acids into urea to decrease body levels of ammonia. Liver work in synthesis of nonessential amino acids and conversion of galactose and fructose to glucose and oxidation of fatty acids. Liver works in conversion of carbohydrates and proteins into fat.
Liver makes modification of waste products, toxic drugs and poisons and synthesis of vitamin A from carotene with the kidney, participation in activation of vitamin D.
Liver manufactures bile salts used in the small intestine for emulsification and absorption of simple fats, lipids and lipo protein liver stores glucose in the form of glycogen and stores fat soluble vitamin A, D, E and K and minerals such as iron from the diet.
Gall bladder:
It is greenish yellow small organ lying near liver. Gall bladder stores greenish fluid called bile that the liver cells continuously produce. Bile is very alkaline and contains pigments, cholesterol, lecithin, mucin, bilirubin and bile salts that act as deterens to emulsify fats (from them into droplets suspended in water) and aid in fat digestion and absorption. Bile alts also combine with the end products of fat digestion to form micelles. Micelles are lipid aggregates (fatty acid and glycerol) with a surface coal of bile salts. Because they are so small, they can cross the microvilli of intestinal epithelium.
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