The 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.
Liver and gall bladder:
The 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.
Metabolic functions:
There is removal of amino acids from organic compounds. There is urea formation from proteins and conversion of excess amino acids into urea to decrease body levels of ammonia. There is manufacture of most of plasma proteins, formation of fetal erythrocytes, and destruction of worm out erhythrocytes and synthesis of blood clotting agents prothrombin and Fibrinogin from amino acids. There is synthesis of non essential amino acids.
There is conversion of galactose and fructose to glucose. There is oxidation of fatty acids. There is formation of lipoproteins, cholesterol and phospholipids (essential cell membrane components). There is conversion of carbohydrates and proteins into fat. There is modification of waste products, toxic drugs and poisons (detoxification). There is synthesis of vitamin A from carotene and with the kidneys, participation in the activation of vitamin D.
There is maintenance of stable body temperature by raising the temperature of the blood passing through it. Its many metabolic activities make the liver the major heat produces in mammal’s body.
There is manufacture of salts which are used in the small intestine for emulsification and absorption of simple fats, lipid and lipoprotein.
Liver stores glucose in the form of glycogen and with the help of insulin and enzymes, converts glycogen back into glucose as the body needs it. Liver also stores fat soluble vitamins (A, D, E and K) and minerals such as iron from the diet. Liver can also store fats and amino acids and convert them into usable glucose as required.
Gall bladder is a small organ near the 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 deterents to emulsify fats from them into droplets suspended in water and aid in fat digestion and absorption. Bile salts also combine with the end products of fat digestion to form micelles. Micelles are lipid aggregates (fatty acids and glycerol) with surface coat of bile salts.
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