 Pancreas is both an exocrine and an endocrine plan. Here we will be discussing the exocrine secretions of pancreas. This diagram is showing the pancreas and the inside of the pancreas also. So, here we see that exocrine pancreas consists of many acinus which open into ducts. This green portion is showing the ducts. Ducts from each acinus join to form main pancreatic duct. This duct opens into deodinum and is surrounded by a sphincter known as sphincter or odi. But before the duct opens into deodinum it is joined by a common bile duct. So, here it is shown that common bile duct is joining the main pancreatic ducts. Just like in salivary glands, both the acinus and ducts of the pancreatic gland contribute to pancreatic exocrine secretion. So, this diagram is showing only the pancreatic ducts and the acinus. Acinar cells secrete juice rich in pancreatic enzymes. While cells lining the duct, secrete watery secretion rich in bicarbonate oil. Pancreatic enzymes digest all meal constituents and they are essential for digestion and absorption of meal constituents, which is not true for gastric enzymes or syripy enzymes. The secretion from duct cells increases deodinal pH because of bicarbonate ions. This is essential for optimum function of pancreatic enzymes and this also prevents damage to deodinal mucosa by acid coming from stomach. So, let us see what are the pancreatic enzymes. The components of meal which need to be digested are carbohydrates, proteins and peptides and fat component. Also, they can be DNA and RNA. Pancreatic acinar secretion consists of enzymes to digest each of these components. These include pancreatic amylase for carbohydrates, for proteins there are two types of enzymes endopeptidase and exopeptidase. Exopeptidases take the last amino acid of the amino acid chain of proteins and while endopeptidases act in between the chain. So, endopeptidases include trypsin and chymotrypsin. While exopeptidases include carboxypeptidase and amylnopeptidases. For pan digestion there is pancreatic lipase and for DNA RNA digestion there are ribonocases. Now, pancreatic amylase and lipase are released in active form. However, proteases are released in inactive form as trypsinogen and chymotrypsinogen. Once these enzymes are secreted by a synarsis and enter into diodenum, trypsinogen is converted to trypsin in diodenum by a diodenal enzyme known as introchymase. So, activation of trypsinogen occurs in diodenum. The activated trypsin then activates other enzymes, other proteases. So, chymotrypsinogen gets converted to chymotrypsin. It is very very important that these proteases are activated only on entering diodenum where they act on meal constituents and not before. Otherwise, they can act on pancreatic parenchyma and blood vessels within it and autodigest the pancreas. Thus, there exist a number of mechanisms which prevent their activation inside the pancreas. These mechanisms include synthesis and storage of proteins as inactive enzymes in chymogen granules. Then, as we have discussed earlier, activation of trypsin occurs only in diodenum by enterokymase and not earlier. Third, along with these enzymes, pancreas also secretes trypsin inhibitors so that in case trypsin is activated in pancreas, it is inhibited. So, till now, we had discussed asynar secretions of the pancreas. Now, let us discuss the mechanism of water secretion and bicarbonate ion secretion by the pancreatic ductor cells. This diagram shows duct cell. Left side is lumen abduct and right side is basolateral site. This mechanism of secretion of bicarbonate is quite similar to secretion of H plus ions in stomach. So, inside the cell, carbon dioxide combines with water, forms H2CO3 in presence of carbonic anhydrase enzyme which dissociates into H plus ions and bicarbonate ions. But in contrast from the stomach, in pancreatic duct cells, these ions move in opposite direction. H plus moves to basolateral site by sodium hydrogen exchanger. Bicarbonate ion moves to lumenal site by bicarbonate chloride exchanger. The chloride reenters into lumen by a chloride channel known as CFTR channel. The sodium ions which have entered into the cell by sodium hydrogen exchanger are thrown out by sodium potassium adase. This is how bicarbonate enters into the lumen of the duct and then water follows passively from the paracellar root.