Functions of various parts of the digestive tract: Accessory Organs

Pancreas: The pancreas is a lobulated organ located in the deodenal loop. It has both endocrine and exocrine functions. Exocrine tissue produces pancreatic juice, which is composed of the digestive enzymes amylase, lipase, and trypsin and sodium bicarbonate. Other salts including potassium, chloride, calcium and magnesium are also present in relatively small quantities. The endocrine system consists of a vascular area called the Islet of Langerhans which secretes the hormones insulin and glucagon. Exocrine secretions drain directly into the duodenum through the pancreatic duct, while endocrine secretions are absorbed into the blood and circulated. Pancreatic enzymes require an optimum pH of 6.9 for their action in the small intestine, which is provided by pancreatic juice. Compared to monogastrics, the pancreatic juice of ruminants has a relatively low bicarbonate content, and therefore the pH of the acidic digesta entering the duodenum increases only slowly. Hence, the initiation of proeolytic activity does not take place immediately in the small intestine of ruminants.
Pancreatic enzymes are classified into three major groups: proteases, amylases and lipases. Among these, proteases are the major enzymes, representing about 72% of the total enzyme secretion. Pancreatic proteases are responsible for protein digestion, so they are also known as protelytic enzymes. Most of the proteolytic enzymes secreted from the pancreas are in inactive form and need to be activated by other enzymes present in the small intestine.
Pancreatic lipase causes hydrolysis of fats into carboxylic acids and glycerols, This action is facilitated by the prior emulsification of fat by the action of bilel salts. In other words, complete hydrolysis of fats in the small intestine is accomplished by the combined action of bile salts and pancreatic lipases. In adult animals, the activity of pancreatic llipase is increased when the animal consumes a high-grain diet. Pancreatic amylase activity is relatively low in ruminants compared to non-ruminants, because most of the starch is fermented in the rumen and little escapes to the small intestine. Pancreastic amylases convert starch into dextrin and maltose (disaccharides) and are of greater sifnificance in starch digestion than the salivary amylases.
Liver and gall bladder: Bile is continuously secreted by the liver. All domestic animals except horses have a gall bladder which serves as a storage organ for bile, which is spoured into the duodenum through the bile duct. In most farm animals, bile and pancreatic secretions are carried into the duodenum through a common duct. In cattle and buffaloes, pancreatic juice and bile are discharged into the duodenum through separate ducts.
Fats entering the small intestine are mostly in the dorm of large globules which cannot be hydrolysed by pancreatic lipases until emulsified by bile salts. Bile contains calcium and potassium salts of flycocholic and taurocholic acids which are required for maintaining alkaline pH and emulsification of fats. In addition to salts, bile also contains pigments (bilirubin and biliverdin), cholesterol, and mucin.
Note: Next Post will Cover The "Large Intestine" of domestic animals.