Physiology of Pancreas Lecture Notes PDF

L4 Physiology of Pancreas GNT Physiology This lecture was presented by: Prof. Mohammed Alzoghaibi & Dr. Hayam Gad Color Index: • Main text • Important • Female Slides • Male Slides • Notes • Extra Editing File Objectives Functional Anatomy of pancreas Major components of pancreatic juice and t...

L4 Physiology of Pancreas GNT Physiology This lecture was presented by: Prof. Mohammed Alzoghaibi & Dr. Hayam Gad Color Index: • Main text • Important • Female Slides • Male Slides • Notes • Extra Editing File Objectives Functional Anatomy of pancreas Major components of pancreatic juice and their physiologic roles Discuss the cellular mechanisms of bicarbonate secretion by the pancreas. Resources Only GI chapters included Cellular mechanisms of enzyme secretion List the proteolytic enzymes synthesized by the pancreas and their target. Describe the mechanism of activation of pancreatic enzymes. Discuss the hormonal & neural mechanisms regulating pancreatic secretion. Potentiation of the secretory response Release, Stimuli & Actions of Secretin & Cholecystokinin Click here for a helpful channel by the team! This is prof sultan meo! Summary of this Lecture will be in the channel soon.. For exocrine pancreas. For endocrine pancreas. ❝ ‫ْض‬ ُ ‫۞ و َ َ رِ ُ ا إ َ ٰ َ ْ ِ َة ٍ ّ ِ رّ ِّ ُ ْ و َ َ ّ ٍ َ ْ ُ َ ا ّ َ و َاتُ و َا ْ ر‬ (133) َ ِ ّ ُ ْ ِ ‫ت‬ ْ ِّ ‫أ‬ ،‫ واﻟﺗﻘرب إﻟﻰ ﷲ ﺑﺄﻧواع اﻟطﺎﻋﺎت؛ ﻟﺗﻧﺎﻟوا ﻣﻐﻔرة ﻣن ﷲ ﻋظﯾﻣﺔ‬،‫وﺑﺎدروا وﺳﺎﺑﻘوا إﻟﻰ ﻓﻌل اﻟﺧﯾرات‬ .‫ َھﯾﱠﺄھﺎ ﷲ ﻟﻠﻣﺗﻘﯾن ﻣن ﻋﺑﺎده‬،‫وﺗدﺧﻠوا ﺟﻧﺔ ﻋرﺿﮭﺎ اﻟﺳﻣﺎوات واﻷرض‬ ‫ﺳر‬ ّ ‫اﻟﺗﻔﺳﯾر اﻟﻣﯾ‬- Functional anatomy Anatomy ● Characteristics ● ● ● ● ● Pancreatic juice is secreted in response to the presence of chyme in the upper portions of the small intestine (duodenum) ● The pancreatic digestive enzymes are secreted by the acini. Large volumes of sodium bicarbonate solution are secreted by the small ductules & larger ducts leading from the acini (from The Pancreas which lies parallel to and beneath the stomach is a large compound (exocrine & endocrine) gland with most of its internal structure similar to that of the salivary glands. The combined product of enzymes & NaCO3 flows through a long pancreatic duct. Pancreatic duct joins the common bile duct immediately before it empties into the duodenum through the papilla of Vater, surrounded by the sphincter of Oddi. Possible SAQ Function duct cells) ● ● ● Volume: 1.2-1.5 L/Day / 1 L/Day Isotonic → The osmolarity of pancreatic fluid = plasma PH: 8 alkaline. Because of bicarbonate solution. ● 1. 2. 3. Pepsin in the duodenum might lead to duodenal ulcer, so we need to neutralize the acidity in the first 3cm of the duodenum. Neutralize the acids in the duodenal chyme to optimum range (pH= 7.0-8.0) for activity of pancreatic enzymes. To prevent damage to duodenal mucosa by acid & pepsin. Produce enzymes for the digestion of carbs, fat & protein. Pancreas divisions Exocrine ● Constitute 99% of pancreas. ● Made of Acinar gland tissue ● The cells lining the acini are serous cells containing zymogen granules → the precursors of pancreatic enzymes (the main source of digestive enzymes). Endocrine Constitute 1% of pancreas Made of Islets of Langerhans. Secretes: hormones directly into the blood. Secretes 3 hormones: 1. Insulin from Beta cells (~60% of Islets cells) 2. Glucagon from Alpha cells (~25%) 3. Somatostatin from Delta cells (~10%) ● 1&2 are crucial for normal regulation of glucose, lipid, and protein metabolism. ● ● ● ● Composition & Mechanism Composition of secretions Organic materials ( 1 - 2 %) ● Mostly enzymes. ● Secreted from: acinar cells. Female slides Inorganic materials ( 1 %) ● Electrolytes. ● Produced from: the centroacinar & intercalated duct cells. ● Include: Na+, K+, Ca++, HCO3- ,Cl-, with greater bulk in the form of NaHCO3 Click here to see the slides’ pictures Mechanism of HCO3- formation Basolateral membrane 1 2 3 4 CO2 and H2O combine in ductal cells to form H2CO3 in the presence of carbonic anhydrase. H2CO3 dissociates into H+ and HCO3H+ is transported into blood by Na+/H+ exchanger at basolateral membrane of ductal cells. Na+/H+ exchanger to work, it needs Na+ into the cell, this happens by Na+/K+ ATPase. HCO3- is secreted into pancreatic juice by Cl-/HCO3exchanger at apical membrane of ductal cells. Cl- pumped into the cell HCO3 - secreted into the lumen. Absorption of H+ causes acidification of pancreatic venous blood (acidic tide) In stomach -> Acid secretion -> Alkaline tide. In pancreas -> Alkaline secretion -> Acidic tide. ‫ وﯾﺻﯾر‬venous blood from stomach ‫ ﺑﻌدھﺎ ﺑﯾﻣر ﻣﻊ‬,Acidic tide ‫"ھو ھﻧﺎ‬ ".‫ ﻣﺎﯾﺗﺄﺛر‬General circulation‫ ﻟﻠـ‬PH ‫ وﻟذﻟك‬Neutralization Extra Explanation from the Leader ‫ ﺣﻠو؟ اﻟﮭﯾدروﺟﯾﻧﮫ‬HCO3‫ ھذا ﻋﻠطول ﺑﯾﺗﻔﻛك إﻟﻰ ھﯾدروﺟﯾﻧﮫ و‬،H2Co3 ‫ ﺑﯾﺣطﮫ ﻣﻊ اﻟﻣوﯾﮫ اﻟﻠﻲ ﻣوﺟودة وﺑﯾﺗﻛون‬CA ‫ ﻓﻲ وﺟود‬،‫ داﺧل اﻟﺧﻠﯾﺔ‬Co2 ‫ﺑﯾدﺧل‬ ‫ ﻣﯾن دﺧﻠﮭﺎ؟‬..‫ ﻟﯾﮫ؟ ﻣﺎ ادري ﻗررت ﺗدﺧل‬،‫ إﺿﺎﻓﯾﺔ‬HCO3 ‫ ﻓﺑﯾدﺧل ﻋﻧدﻧﺎ‬transporter ‫ ﺑﺗﻼﺣظون ﻓوق ﻓﯾﮫ‬،‫اﻧﺳوھﺎ ﺷوي‬ .secodary Active transport ‫ ﻟذﻟك ﺗﻌﺑﺗر‬Na ‫اﻟـ‬ ‫ ھل ﺑﻧﻘدر‬Cl‫ ﯾﻌﻧﻲ ﺧﻠص اﻟـ‬،‫ طﯾب ﺗﺧﯾﻠوا ان ﻛل اﻟﻛﻠوراﯾد دﺧل ﺟوا‬،‫ ﻋﺷﺎن ﺗﻘدر ﺗطﻠﻊ‬Cl ‫ ﺑس ﻧﺣﺗﺎج ﻧدﺧل‬luminal border ‫ ﺑﺗطﻠﻊ ﻟﻠـ‬HCO3‫اﻵن اﻟـ‬ .recycling ‫ ﯾﺻﯾر ﻟﮫ‬Cl ‫ ﻋﺷﺎن ﻛذا‬،‫؟ ﻻ‬HCO3 ‫ﻧطﻠﻊ‬ ‫ وھذا ﻣﻧطﻘﻲ ﻷن اﺣﻧﺎ ﻧﺑﻐﻰ‬lumen ‫ ﻟﻠدم وﻟﯾس‬Basolateral border ‫اﻟﮭﯾدروﺟﯾﻧﮫ اﻟﻠﻲ ﻗﻠت اﻧﺳوھﺎ وﯾن ﺑﺗروح؟ ﻣﮭم ﺟداً ﻧﻌرف اﻧﮭﺎ ﺑﺗروح ﻟﺟﮭﺔ‬ ً‫ ﺑﻛل ﺑﺳﺎطﺔ )ﻣﻣﻛن ﺑﻌﺿﻛم ﯾﺳﺄل ﻟﯾﮫ ﻣﺎﯾﺻﯾر ﻣﺛﻼ‬Acidic tide ‫ ﺣﻠو؟ وھذا ﺳﺑب‬,stomach‫ اﺣﻧﺎ ﺑﺎﻟﺑﻧﻛرﯾﺎس ﻣو ﺑﺎﻟـ‬Alkaline solution .(‫ اﻟﺳﺑب ھو اﻟﻧوت اﻟﻠﻲ ﻓوق ﺣﻘت اﻟدﻛﺗور‬،Metabolic Acidosis (‫ ﻟﻠﺻودﯾوم‬recycling ‫ ﺑﻧﺣﺗﺎج ﻧﺳوي‬،‫وطﺑﻌﺎ ً ﻋﺷﺎن ﻧطﻠﻊ اﻟﮭﯾدروﺟﯾﻧﮫ ھﺎذي ﺑﻧدﺧل ﺻودﯾوم )وﻧﻔس ﻓﻛرة اﻟﻛﻠوراﯾد ﺑﺎﻟﺿﺑط‬ Completely isosmotic bicarbonate solution ،‫ وھذا ﺳﺑب ان ﻣﺎﻓﯾﮫ ﻓرق ﻣﻊ اﻟﺑﻼزﻣﺎ‬Osmosis‫ﺑﺎﻟﻧﺳﺑﺔ ﻟﻠﻣوﯾﺔ ﺑﺗدﺧل ﺑﺎﻟـ‬ Important Luminal Border Effect of flow Rate on pancreatic secretion The increase in the pancreatic secretion rate (Secretion velocity): 1. 2. 3. ↑ HCO3 ↓ClNa+ & K+ remain the same in plasma & pancreatic juice Lumen side (Pancreatic duct) Everything in this pic was mention by the Dr. pancreatic secretions Phases of pancreatic secretions Phase Cephalic Phase 20% of pancreatic secretion Will be affected in case of vagotomy Stimulus Mediator ● ● ● ● Smell, Hearing* Swallowing Taste Chewining Ach by the vagal nerve Gastric Phase 5-10% of pancreatic secretion Will be affected in case of vagotomy Intestinal Phase 70-75% of pancreatic secretion ● ● Gastric distention Presence of proteins ● ● Fatty acids Acidity of the chyme (H+) ● ● Vago-vagal reflex Ach by the vagal nerve ● Secretin CCK Vago-vagal reflex * Due to presence of food in the mouth or even in abcense of food in the mouth, eg, Hearing sounds of food preparation! And this is called conditional reflex. ● ● What’s the conditional Reflex? : ‫ﻛﻧت ﺑﺷرﺣﮭﺎ ﺑس ﻣﺎﻓﻲ أﺣﺳن ﻣن دﻛﺗور ﻧﺎﺟﻲ‬ 45:50 :‫اﻟدﻗﯾﻘﺔ‬ Secretions ● Pancreatic secretions contain many enzymes for digesting proteins, carbohydrates, fats & large quantities of HCO3 ions. Proteins Endopeptidases: - Trypsin - Chymotrypsin Exopeptidases: - Carboxypeptidase Fat - Pancreatic lipase - Cholesterol esterase (Carboxyl Ester hydrolase) - Phospholipase DNA & RNA Nucleases - Ribonuclease - Deoxyribonuclease Carb - Pancreatic amylase Click for a summary from the female slides “Please don’t skip” The Role of Pancreas in Digestion Carbohydrates The pancreatic enzyme for digesting carbohydrates is pancreatic amylase, which hydrolyzes starches, glycogen and most other carbohydrates (except cellulose) to form mostly disaccharides (maltose) and a few tri-saccharides. ● Carbs in diet Polysaccharides Disaccharides Starch 𝝰- amylase 𝝰- Dextrins 𝝰- Dextrinase Maltose Maltotriose Maltase Sucrase Sucrose Lactose Trehalose Sucrase Lactase Trehales Glucose + Fructose Glucose + Galactose Glucose Glucose Enterocytes = cells of the doud. And jejunum Brush border secrets these enzymes in the duodenum and jejunum Fats ● The main enzymes for fat digestion are: Pancreatic lipase, Cholesterol esterase & Phospholipase. -Pancreatic lipase: is the most important fat splitting enzyme. It breaks TG into MG and 2 FAs in the presence of bile salts and colipase. -Cholesterol esterase: which liberates cholesterol and FA. -Phospholipase A2 :which splits phospholipids into lysolecithin & FA. Fat in diet Cholesterol ester Triglycerides Lingual & pancreatic lipases Cholesterol ester hydrolase Cholesterol + Fatty acid Monoglyceride + 2 Fatty acids Phospholipid Phospholipase A2 Lysolecithin + Fatty acid Pancreatic lipase work in the presence of bile salts & colipase Female slides Nucleic Acid Deoxyribonucleases DNA & RNA Ribonucleases Mononucleotides (the basic building block of nucleic acid) The Role of Pancreas in Digestion Cont. The suffix -ogen or prefix pro- indicates the enzyme is secreted in an inactive form Protein The most important pancreatic enzymes for digesting proteins are: Trypsin, Chymotrypsin and Carboxypolypeptidase. Trypsin ● Synthesis ● ● Activation ● ● Chymotrypsin When first synthesized in the pancreatic cells, the proteolytic digestive enzymes are in the inactive forms: Trypsinogen, Chymotrypsinogen and Procarboxypolypeptidas. They become activated only after the are secreted into the intestinal tract. Trypsinogen is activated by Enteropeptidase (enterokinase), an enzyme secreted by the intestinal mucosa when chyme comes in contact with the mucosa. Trypsinogen can be activated autocatalytically by trypsin formed from previously secreted trypsinogen. The most important pancreatic enzyme to be activated. ● Chymotrypsinogen and Procarboxypeptidase are activated by trypsin to form chymotrypsin and carboxypolypeptidase. ● Trypsin & Chymotrypsin (Endopeptidases) → Split whole and partially digested proteins into peptides of various sizes. ● Do not cause release (break down) of individual amino acids. Function Trypsinogen 1 Enterokinase 2 3 Trypsin Inactive (precursor) Carboxypolypeptidase ● Carboxypeptidase (Exopeptidases) → Splits some peptides into individual amino acids at the carboxyl terminus → completing the digestion of some proteins to amino acids Chymotrypsinogen Chymotrypsin Proelastase Elastase Prophospholipase A Phospholipase A Procarboxypeptidase A or B Carboxypeptidase A or B Active Important 1- Enterokinase is an enzyme that is secreted by brush border of small intestine and activate trypsinogen. 2- Trypsin autocatalytically activates itself to active other trypsinogen, and other enzyme. **If it gets inhibited (trypsin) all of these enzymes will stop working (inactive) Peptide ● Important Trypsin Inhibitor Secretion of Trypsin Inhibitor Prevents Digestion of the Pancreas Itself. How? 1 Proteolytic enzymes of the pancreatic juice do not become activated until after they have been secreted into the intestine because the trypsin and the other enzymes would digest the pancreas itself. 2 The same cells that secrete proteolytic enzymes into the acini of the pancreas secrete another substance called trypsin inhibitor, which is formed in the cytoplasm of the glandular cells 3 It prevents activation of trypsin both inside the secretory cells and in the acini and ducts of the pancreas. 4 Because trypsin activates the other pancreatic proteolytic enzymes, therefore trypsin inhibitor prevents activation of the other enzymes as well. 5 When a duct is blocked, trypsin inhibitor can not inhibit activation of accumulated enzymes which will be activated and digest the pancreas in few hours. Female slides Clinical application: acute pancreatitis Accumulation of the enzymes in the pancreas due to obstruction or other cause (e.g. zollinger-ellison), will lead autoactivation of pancreatic enzymes inside the pancreas, leading to acute pancreatitis Multiplicative / Potentiation Effect When all different stimuli of pancreatic secretion (acetylcholine, cholecystokinin, and secretin) occur at once, then the total secretion is far greater than the sum of the secretions caused by each stimulus separately. The stimuli are said to “multiply” or “potentiate” one another. Usually, pancreatic secretions are the result of multiple stimuli rather than one stimulus. Example: ● Ach alone: 2 ● CCK alone: 3 ● Secretin alone: 2 ● Total secretion is Not the sum (7)! These stimuli are said to multiply/ potentate eg(12) (numbers are random, just to get the idea) Important Regulation of Pancreatic Secretion 1. Vagus nerve 3. Secretin 2. Cholecystokinin (CCK) -Act on acinar cells. -Functions: Acetylcholine from parasympathetic vagus nerve endings and from other cholinergic nerves in the enteric nervous system → 1) increase in enzyme secretion-fluid & HCO-3. 2) Vagus nerve stimulation relaxes (opens) the sphincter of Oddi → release pancreatic enzymes. -Act on activating acinar cells -Secreted by: I cells in the duodenal (enteroendocrine cells) & jejunal mucosa. -Stimulated by: food entering the small intestine containing: 1)Fat (long-chain fatty acids). 2)Proteoses & peptides (Partial protein degradation products). -Function: ↑Pancreatic digestive enzymes CCK: relaxes sphincter of Oddi. Most powerful hormone acting on sphincters. - Ach & CCK stimulate the acinar cells of the pancreas, causing production of large quantities of pancreatic digestive enzymes but relatively small quantities of H2O & electrolytes to go with the enzymes. -Secretin: When acid chyme with PH less than 4.5-5 enters the duodenum from the stomach, it causes duodenal mucosal release and activation of secretin, which is then absorbed into the blood. - Secretin (in contrast) stimulates secretion of large quantities of H2O and NaHCO3 solution by the pancreatic ductal epithelium. Trypsin inhibitors (TI) get degraded in the duodenum to let the trypsin function. After secretin secretion, it is then absorbed into the blood. Cholecystokinin, like secretin, passes by way of the blood to the pancreas Cholecystokinin (CCK) Information This effect is similar to that caused by vagal stimulation but even more pronounced, accounting for 70-80% of the total secretion of the pancreatic digestive enzymes after a meal. ● ● ● ● Function ● ● ● -Act on activating ductal cells -Secreted by: S cells in duodenal & upper jejunal mucosa (present as presecretin). Stimulated by: increased chyme acidity in the duodenum and jejunum luminal pH < 4.5 -Function: stimulate secretion of large quantities of H2O and NaHCO3 solution from ductal cells → neutralize chyme acidity. The secreted HCO3 concentration = 145 mmol/L ~5X normal but a low concentration of Cl-. HCl + NaHCO3 → NaCl + H2CO3 H2CO3 → CO2 + H2O Augments stimulation of HCO3- & H20 secretion by secretin. Stimulates pancreatic enzyme secretion. Stimulates intestinal motility & relaxes ileocecal sphincter. Inhibits stomach contraction moderately & slows its emptying. Contracts gallbladder, relaxes sphincter of Oddi and causes bile discharge into intestine. Has trophic effect on pancreas. Maybe concerned with the mechanism of satiety. Secretin Important Secretin is present in an inactive form:prosecretin ● ● ● ● ● ● Augments stimulation of enzyme secretion by CCK. Stimulates pancreatic secretion rich in HCO3- & H20 from duct cells. Stimulates hepatic bile flow & HCO3secretion Inhibits gastric acid secretion & gastrin release, but it stimulates pepsin secretion. Inhibits gastric motility, contracts pylorus & slows gastric emptying, relaxes LES. Inhibits intestinal motility & contracts ileocecal sphincter. Cell types of the pancreas: Ductal cells Acinar cells Secretes a HCO3- rich fluid that alkalinizes & hydrates (H2O) the protein-rich secretion of acinar cells [HCO3-] = 145 mEq/L. Secrete a protein-rich (digestive enzymes) secretion in an isotonic plasma-like fluid (so enzymes will be thick in absence of ductal cells effect). Because there is high amount of enzymes secreted from acinar cells in a little solution, it’s thick → needs solution to facilitate its move until they arrive to the duodenum to prevent duct blockage → this solution is provided by ductal cells ● Constitute 75% of pancreatic secretion. ● Constitute 25% of total pancreatic secretion. ● Stimulated by Secretin secreted by S cells. ● Stimulated by CCK secreted from I cells & Ach. ● Effects of Secretin are potentiated by CCK & Ach. ● When all these different stimuli of pancreatic secretion occur at once, then the total secretion is far greater than the sum of the secretions caused by each stimulus separately. ● The stimuli are said to “multiply” or “potentiate” one another. Why don’t these enzymes digest the pancreas? • Secreted as proenzymes (inactive form) which get activated in the lumen of the intestine. If they one of enzyme activated in the pancreas for any reason trypsin inhibitor will do its role of protection. • The same cells secrete a substance “trypsin inhibitor”. Pictures from the slides Neural and Hormonal Control of Pancreatic Secretion Regulation by Secretin Regulation by CCK Doctors’ Notes 1: The Main pancreatic duct joins the duct from the liver (common bile duct) and both of them open in 2nd portion of duodenum through “papilla of vater” surrounded by Oddi sphincter. 2:Sphincter of Oddi is regulated by CCK: 𖤐Relax it -> secretions goes into duodenum. 𖤐Also squeeze the bile duct and pancreatic duct -> release components into duodenal lumen. 3:Major functions of pancreatic secretions: 1-Neutralise acid in “duodenal ” chyme, 𖤐Possible SAQ, what’s the importance of that? 1-To prevent damage to duodenal mucosa. 2-To provide optimal PH for action of intestinal enzymes. 𖤐What’s the main source of digestive enzymes of GIT? Pancreas! Because it produce enzymes for all types of food stuff (proteins,carb,etc..) 4:All gastrointestinal secretions are: Isosmotic Except (saliva, Hyposmotic) salivary=Hyposmotic‫اﻟدﻛﺗور واﻟدﻛﺗوره ﻛﻠﮭم ﻗﺎﻟوا ﻣﻌﻠوﻣﺔ اﻟـ‬ 5:Enteropeptidase is brush border enzyme and it’s NOT in pancreatic tissue/duct! 𖤐Only trypsinogen is (Auto-catalytically) activated. 𖤐Key reaction in activation of pancreatic proteolytic enzymes is the: Release of trypsin 6:Pancreatic Amylase:hydrolyse carbs to —> MALTOSE (disaccharide) “Pancreatic amylase vs salivary amylase Which one of them is more powerful? Both have same potency but in the mouth food stays for short duration (not sufficient for the activity of the enzyme) ,So pancreatic amylase has physiological importance because food(chyme) stays for sufficient time for the action of pancreatic amylase “ “Gastric Lipase - pancreatic lipase - intestinal lipase, Which is more sufficient? Pancreatic Lipase, ‫ ﻷﻧﮫ اذا ﻗل‬-> loss of fat in stool” 𖤐More activation of pancreatic acinar cells -> more production of isotonic solution in ductal cells . :‫ وﻣوﺟوده ﺑﺷﻛل ﻣﺷﺎﺑﮫ ﺑﺳﻼﯾدات اﻟدﻛﺗورة‬،‫ھﺎذي ﻧوت اﻟدﻛﺗور‬ "Hco3 conc. increases with increasing secretion rate" 7:Secretin and CCK: .‫ ﺗﻧﺣﻔظ‬site of release /stimulus/ action :‫اﻟدﻛﺗورة‬ ”‫ "ھذا ﻣن اﻟﺟدول ﺣﻘﻲ اﻟﻠﻲ ھو ﺟزء ﻣن ﺣﯾﺎﺗﻲ وﺣﯾﻛون ﺟزء ﻣن ﺣﯾﺎﺗك ﻏﺻﺑﺎ ً ﻋﻧك‬:‫اﻟدﻛﺗور‬ ‫أي ﺟدول؟ھﻧﺎ‬ 8:Functions of Secretin: "ً‫ "ھذا ﻣﮭم اوي اوي ﯾﻌﻧﻲ ﺗﻌرﻓوه ﻛوﯾس ﺟدا‬:‫اﻟدﻛﺗورة‬ 9:Functions of CCK: This function is so important: Contracts Gall bladder, Relaxes sphincter of Oddi. TEST YOURSELF ! MCQ: Q1) Pancreatic secretion is stimulated by? B) Secretin A) CCK C) Vagal stimulation D) all of them C) autocatalytically D) A+C Q2) Trypsinogen is activated by? A) Enteropeptidase B) Exopeptidases Q3) Which of the following is a function of the pancreas? A) increase acidity of chyme B) produce enzymes involved in digestion C) secrets mucin to protect duodenal lining D) storage of digestive enzymes Q4) What’s the type of secretion pancreatic acini produces? B) hypotonic A) isotonic C) hypertonic D) acidic Answers: Q1:D | Q2:D | Q3:B | Q4:A SAQ: Q1) Give two examples of enzymes for each of the following classification of pancreatic enzymes: A) proteolytic enzymes: B) Amylolytic enzymes : C) Nuceolytic enzymes: 1. 2. 1. 2. 1. 2. endopeptidases carboxypeptidases A and B Alpha-Amylase Lipases Ribonuclease Deoxyribonuclease Q2) Compare between phases of pancreatic secretions? Phase Cephalic Gastric Intestinal Stimulus Smell, taste, chewing, swallowing Protein, Gastric distention Fatty acid, acidity in chyme Mediator Neural (Vagus nerve ) Neural (Vagus nerve “Vago-vagal reflexe”) Hormonal stimulus (CCK, Secretin), Neural(vagus nerve “vago-vagal reflex”). The BEST Team Leaders Rafan Alhazzani Fahad Almughaiseeb Ghaida Aldossary Faisal Alzuhairy Team Members Sarah Alshahrani Hamad Alziyadi mansour Alotaibi Melaf Alotaibi Nazmi A Alqutub Layan aldosary Raghad Almuslih Nazmi M Alqutub Norah alhazzani Layla Alfrhan khalid Alanezi Jouri Almaymoni Lama Almutairi Abdulaziz abahussain Salma Alkhlassi Remas mohammed Yousof Badoghaish Shoug Alkhalifa