Pancreas_functional anatomy_enzymes.pptx

Pancreas functional anatomy

1. Pancreas Dr. C. Kalyan, Dr. E. Muralinatb , Dr. M. Ambika prasad , Dr. K.S. Sravan Pragna. Dr P. Manjari & Dr. R. Gnana lahari

2. FUNCTIONAL ANATOMY AND NERVE SUPPLY OF PANCREAS Pancreas is a dual organ and it consists of two functions, such as endocrine function and exocrine function. Endocrine function is related to the production of hormones . The exocrine function is associated with the secretion of digestive juice termed as pancreatic juice

3. FUNCTIONAL ANATOMY OF EXOCRINE PART OF PANCREAS Exocrine part of pancreas resembles salivary gland regarding structure. It is made up of acini or alveoli. Each acinus c onsists of a single layer of acinar cells along with a lumen in the center. 4) Acinar cells con sist of zymogen granules, which possess digestive enzymes. A small duct arises from lumen of each alveolus. Some of these ducts from neighboring alveoli give rise to form intralobular duct.

4. All the intralobular ducts unite to form the main duct of pancreas termed as Wirsung duct. 7) Wirsung duct joins common bile duct to form ampulla of Vater, which opens into duodenum In some persons, an accessory duct called duct of Santorini persists . It also opens into duodenum, proximal to the opening of ampulla of Vater.   i. High bicarbonate content makes the pancreatic juice highly alkaline, so that it priovides the ptotection to the intestinal mucosa from acid chyme by neutralizing it   ii. Bicarbonate ions arrange the required pH (7 to 9) particularly for the activation of pancreatic enzymes.

5. NERVE SUPPLY TO PANCREAS Pancreas is supplied by both sympathetic and parasympathetic fibers. Sympathetic fibers are supplied through splanchnic nerve and parasympathetic fibers are supplied through vagus nerve. . High bicarbonate content of pancreatic juice is important because of two reasons:  

6. PROPERTIES OF PANCREATIC JUICE Volume : 500 to 800 mL/day Reaction : Highly alkaline with a pH of 8 to 8.3 Specific gravity : 1.010 to 1.018 COMPOSITION OF PANCREATIC JUICE Pancreatic juice con sists of 99.5% of water and 0.5% of solids. The solids are the organic and inorganic substances.Bicarbonate content is very high in pancreatic juice. 3) It is about 110 to 150 mEq/ L, against the plasma level of 24 mEq/L.

7. FUNCTIONS OF PANCREATIC JUICE Pancreatic juice has digestive functions and neutralizing action. DIGESTIVE FUNCTIONS OF PANCREATIC JUICE Pancreatic juice plays an important role regarding the digestion of proteins and lipids. It also exhibits mild digestive action on carbohydrates. DIGESTION OF PROTEINS Major proteolytic enzymes of pancreatic juice are try psin and chymotrypsin. Other proteolytic enzymes are carbo­ xypeptidases, nuclease, elastase and collagenase.

8. 1. Trypsin Trypsin is a single polypeptide with a molecular weight of 25,000. It con sists of 229 amino acids. I t is secreted as inactive trypsinogen, which is c hanged into active trypsin by enterokinase. Enterokinase is also termed as enteropeptidase and it is secreted by the brush­bordered cells of duodenal mucus membrane. Once formed, trypsin itself stimulates trypsinogen with the help of autocatalytic or autoactive action.

9. Trypsin inhibitor Trypsinogen is stimulated only if it arrives the small intestine. If trypsin is activated if it is in pancreas, it may hydrolyze the pancreatic tissue proteins, leading to in pancreatic damage. But its activation in the secretory cells, acini and ducts of pancreas is inhibited by an inhibitor protein termed as trypsin inhibitor. Any abnormality or deficiency of the trypsin inhibitor will lead to unopposed trypsin activity, which damages the pancreas.

10. Actions of trypsin i. Digestion of proteins: Trypsin is the most powerful proteolytic enzyme. It is an endopeptidase and breaks the interior bonds of the protein molecules and c hanges proteins into proteoses and polypeptides   ii. Curdling of milk: It c hanges caseinogen in the milk into casein   iii. Blood clotting: It enhances blood clotting  

11. iv. It stimulates the other enzymes of pancreatic juice, viz. a. Chymotrypsinogen into chymotrypsin b. Procarboxypeptidases into carboxypeptidases c. Proelastase into elastase d. Procolipase into colipase v. Trypsin also activates collagenase, phospholi pase A and phospholipase B vi. Autocatalytic action: Once formed, trypsin itself converts trypsinogen into trypsin.

12. 2. Chymotrypsin Chymotrypsin is a polypeptide with a molecular weight of 25,700 and 246 amino acids. It is secreted in the form of inactive chymotrypsinogen, which is particularly activated into chymotrypsin by trypsin. Actions of chymotrypsin i. Digestion of proteins: Chymotrypsin is also an endopeptidase and it c hanges proteins into polypeptides   ii. Digestion of milk: Chymotrypsin digests casein i gen faster compare to trypsin. Combination of both enzymes causes rapid digestion of milk iii. On blood clotting: A ction. is not see.

13. 3. Carboxypeptidases A) Carboxypeptidases are carboxypeptidase A and carboxypeptidase B. B) Carboxypeptidase A is derived from the precursor procarboxypeptidase A. C) Carboxypeptidase B is derived from procarboxypeptidase B. Procarboxypeptidases are activated into carboxypeptidases by trypsin.   Actions of carboxypeptidases A) Carboxypeptidases are exopeptidases and break the terminal bond of protein molecules. B) Exopeptidases split the polypeptides and other proteins into amino acids. C) Carboxypeptidase A splits the proteins into amino acids having aromatic or aliphatic side chains. Carboxypeptidase B c hanges the proteins into amino Acids along with basic side chains.

14. 4. Nucleases A) Nucleases of pancreatic juice are ribonuclease and deoxyribonuclease, which play an important role regarding the digestion of nucleic acids. B) These enzymes convert the ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) into mononucleotides.   5. Elastase Elastase is secreted in the form of inactive proelastase, which is activated into elastase with the help of trypsin. Elastase digests the elastic fibers.  

15. 6. Collagenase Collagenase is secreted as inactive procollagenase, which is converted into collagenase with the help of trypsin. It digests collagen.