Pancreatic Physiology L4
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Questions and Answers

What is the main function of Cholecystokinin (CCK) in pancreatic secretion?

  • Stimulate hepatic bile flow & HCO3 secretion
  • Stimulate secretion of large quantities of H2O and NaHCO3 solution from ductal cells
  • Relax the sphincter of Oddi to release pancreatic enzymes
  • Increase enzyme secretion and fluid & HCO3 from acinar cells (correct)

    • What is the main function of Secretin in pancreatic secretion?

  • Relax the sphincter of Oddi to release pancreatic enzymes
  • Stimulate secretion of large quantities of H2O and NaHCO3 solution from ductal cells (correct)
  • Stimulate hepatic bile flow & HCO3 secretion
  • Increase enzyme secretion and fluid & HCO3 from acinar cells

    • Which cell type constitutes 75% of pancreatic secretion?

  • Endocrine cells
  • Ductal cells
  • Islet cells
  • Acinar cells (correct)

    • What happens when acid chyme with PH less than 4.5-5 enters the duodenum from the stomach?

    <p>Causes duodenal mucosal release and activation of secretin</p> Signup and view all the answers

    What is the role of trypsin inhibitor in preventing digestion of the pancreas?

    <p>Inhibits activation of trypsin in the pancreas</p> Signup and view all the answers

    What is the main effect of Cholecystokinin (CCK) on the sphincter of Oddi?

    <p>Relaxes it to release pancreatic enzymes into duodenum</p> Signup and view all the answers

    Which of the following is a major component of pancreatic juice?

    <p>Bicarbonate</p> Signup and view all the answers

    What are the proteolytic enzymes synthesized by the pancreas primarily responsible for?

    <p>Digesting proteins</p> Signup and view all the answers

    What is the cellular mechanism of bicarbonate secretion by the pancreas?

    <p>Chloride-bicarbonate exchange</p> Signup and view all the answers

    Which hormones are involved in regulating pancreatic secretion?

    <p>Secretin &amp; Cholecystokinin</p> Signup and view all the answers

    What is the mechanism of activation of pancreatic enzymes?

    <p>Conversion of trypsinogen to trypsin</p> Signup and view all the answers

    What is the primary function of the exocrine pancreas?

    <p>Production of digestive enzymes and bicarbonate</p> Signup and view all the answers

    Which enzyme is responsible for activating trypsinogen?

    <p>Enteropeptidase</p> Signup and view all the answers

    What phase of pancreatic secretion is stimulated by the presence of food in the intestine?

    <p>Intestinal Phase</p> Signup and view all the answers

    Which phase of pancreatic secretion is reduced in case of vagotomy?

    <p>Gastric Phase</p> Signup and view all the answers

    What are the inactive forms of the proteolytic digestive enzymes?

    <p>$Trypsinogen$, $chymotrypsinogen$, and $procarboxypeptidase$</p> Signup and view all the answers

    What substance prevents digestion of the pancreas itself?

    <p>$Trypsin$ $inhibitor$</p> Signup and view all the answers

    Which enzyme is responsible for fat digestion?

    <p>$Pancreatic$ $lipase$</p> Signup and view all the answers

    What is the primary function of the exocrine pancreas?

    <p>Producing organic and inorganic secretions in response to food in the duodenum</p> Signup and view all the answers

    What is the role of the islets of Langerhans?

    <p>Secreting hormones directly into the bloodstream</p> Signup and view all the answers

    What is the main component of pancreatic juice for neutralizing acidic chyme?

    <p>$HCO3-$</p> Signup and view all the answers

    Which cells are responsible for secreting pancreatic enzymes?

    <p>Acinar cells</p> Signup and view all the answers

    What is the function of the basolateral membrane of the ductal cells in pancreatic secretion?

    <p>$Na^+$/H$^+$ exchanger and $Na^+$/K$^+$ ATPase to transport $Na^+$ into the cell</p> Signup and view all the answers

    What happens to the pancreatic secretion rate with an increase in secretion velocity?

    <p>Increases with an increase in secretion velocity</p> Signup and view all the answers

    Which of the following is the key reaction in the activation of pancreatic proteolytic enzymes?

    <p>Release of trypsin</p> Signup and view all the answers

    Which enzyme is more powerful, pancreatic amylase or salivary amylase?

    <p>Pancreatic amylase</p> Signup and view all the answers

    Which lipase is more efficient in fat digestion?

    <p>Pancreatic lipase</p> Signup and view all the answers

    What happens with an increase in activation of pancreatic acinar cells?

    <p>More production of isotonic solution in ductal cells</p> Signup and view all the answers

    'Hco3' concentration increases with increasing secretion rate' is associated with which hormones?

    <p>Secretin and CCK</p> Signup and view all the answers

    What are the functions of CCK?

    <p>Stimulates pancreatic enzyme secretion, contracts gall bladder</p> Signup and view all the answers

    Which of the following is a function of the pancreas?

    <p>Produce enzymes involved in digestion</p> Signup and view all the answers

    What type of secretion do pancreatic acini produce?

    <p>Isotonic</p> Signup and view all the answers

    Which hormone stimulates the secretion of pancreatic juice?

    <p>All of them</p> Signup and view all the answers

    Which enzyme activates trypsinogen?

    <p>Enteropeptidase</p> Signup and view all the answers

    What is the key reaction in the activation of pancreatic proteolytic enzymes?

    <p>Release of trypsin</p> Signup and view all the answers

    Which phase of pancreatic secretion is stimulated by fatty acids and acidity in chyme?

    <p>Intestinal phase</p> Signup and view all the answers

    What is the primary function of the exocrine pancreas?

    <p>Production of organic and inorganic secretions in response to food</p> Signup and view all the answers

    What is the main component of pancreatic juice for neutralizing acidic chyme?

    <p>Sodium bicarbonate solution</p> Signup and view all the answers

    What happens to the pancreatic secretion rate with an increase in secretion velocity?

    <p>Increase in HCO$_3^-$ secretion and decrease in Cl$^-$, Na$^+$, and K$^+$ secretion</p> Signup and view all the answers

    What is the cellular mechanism of bicarbonate secretion by the pancreas?

    <p>Active transport of HCO$_3^-$ by ATPase pumps</p> Signup and view all the answers

    Which hormones are involved in regulating pancreatic secretion?

    <p>$HCO_3^-$ and insulin</p> Signup and view all the answers

    What is the role of the basolateral membrane of the ductal cells in pancreatic secretion?

    <p>Actively transporting $Na^+$ into the cell to aid $HCO_3^-$ secretion</p> Signup and view all the answers

    Which phase of pancreatic secretion is triggered by gastric distention and the presence of proteins, fatty acids, and acidity of the chyme?

    <p>Gastric Phase</p> Signup and view all the answers

    What is the main function of enteropeptidase in pancreatic secretion?

    <p>Activating trypsinogen</p> Signup and view all the answers

    Which enzyme prevents the digestion of the pancreas itself?

    <p>Trypsin inhibitor</p> Signup and view all the answers

    What can lead to autoactivation and acute pancreatitis due to the accumulation of enzymes in the pancreas?

    <p>Obstruction in the bile duct</p> Signup and view all the answers

    Which phase accounts for 20% of pancreatic secretion and is stimulated by smell, hearing, and swallowing?

    <p>Cephalic Phase</p> Signup and view all the answers

    Which enzyme is responsible for fat digestion?

    <p>Pancreatic lipase</p> Signup and view all the answers

    What is the primary function of the exocrine pancreas?

    <p>Production of digestive enzymes and bicarbonate to aid in digestion</p> Signup and view all the answers

    Which hormone is primarily responsible for stimulating the secretion of pancreatic enzymes?

    <p>Secretin</p> Signup and view all the answers

    What is the main component of pancreatic juice for neutralizing acidic chyme?

    <p>Bicarbonate ions</p> Signup and view all the answers

    Which phase of pancreatic secretion is reduced in case of vagotomy?

    <p>Cephalic phase</p> Signup and view all the answers

    What is the cellular mechanism of bicarbonate secretion by the pancreas?

    <p>$\text{HCO}_3^-$ ions are secreted by ductal cells in exchange for Cl$^-$ ions</p> Signup and view all the answers

    Which hormone stimulates the release of bile from the gallbladder and pancreatic juice from the pancreas?

    <p>Cholecystokinin (CCK)</p> Signup and view all the answers

    Which of the following stimuli does NOT contribute to the release of pancreas secretions?

    <p>Gastric distention</p> Signup and view all the answers

    What is the main function of CCK in pancreatic secretion?

    <p>Stimulates release of digestive enzymes from acinar cells</p> Signup and view all the answers

    What is the main function of secretin in the pancreas?

    <p>Stimulates release of H2O and NaHCO3 solution from ductal cells</p> Signup and view all the answers

    Which statement about pancreatic secretions is true?

    <p>HCO3- concentration is much higher than Cl- concentration</p> Signup and view all the answers

    What is the role of enteropeptidase in pancreatic secretion?

    <p>Activates trypsinogen to trypsin</p> Signup and view all the answers

    What is the main function of the sphincter of Oddi in pancreatic secretion?

    <p>To regulate the release of components into the duodenal lumen</p> Signup and view all the answers

    Study Notes

    • The pancreas is a large compound gland located beneath the stomach, with exocrine and endocrine functions.

    • Exocrine pancreas produces organic secretions (primarily enzymes) and inorganic secretions (electrolytes) in response to food in the duodenum.

    • Endocrine pancreas consists of islets of Langerhans, which secrete hormones directly into the bloodstream.

    • Pancreatic juice contains a large amount of sodium bicarbonate solution to neutralize acidic chyme in the duodenum.

    • Pancreatic enzymes are secreted by acinar cells, which contain zymogen granules.

    • The islets of Langerhans produce three hormones: insulin, glucagon, and somatostatin, which regulate glucose, lipid, and protein metabolism.

    • HCO3- is formed in the pancreatic ductal cells by the combination of CO2 and H2O, with the help of carbonic anhydrase, and is secreted into the pancreatic juice by an apical membrane transporter.

    • The basolateral membrane of the ductal cells uses an Na+/H+ exchanger and Na+/K+ ATPase to transport Na+ into the cell, which is necessary for the HCO3- secretion process.

    • The pancreatic juice is an isosmotic bicarbonate solution that plays a crucial role in the digestion and absorption of food in the small intestine.

    • The pancreatic secretion rate increases with an increase in secretion velocity, which leads to an increase in the amount of HCO3- secreted and a decrease in the amount of Cl-, Na+, and K+, while maintaining the same concentration in the plasma and pancreatic juice.

    • Pancreatic secretions contain various enzymes for digesting proteins, carbohydrates, fats, and large quantities of HCO3 ions.

    • Three phases of pancreatic secretion: Cephalic, Gastric, and Intestinal.

    • Cephalic Phase: stimulated by smell, hearing, and swallowing. Accounts for 20% of pancreatic secretion.

    • Gastric Phase: triggered by gastric distention and presence of proteins, fatty acids, and acidity of the chyme. Accounts for 5-10% of pancreatic secretion.

    • Intestinal Phase: initiated by the presence of food in the intestine. Accounts for 70-75% of pancreatic secretion.

    • Gastric Phase secretion is reduced in case of vagotomy.

    • Pancreatic enzymes for carbohydrate digestion include pancreatic amylase and maltase.

    • Pancreatic enzymes for fat digestion include pancreatic lipase, cholesterol esterase, and phospholipase.

    • Trypsin, chymotrypsin, and carboxypeptidase are the most important pancreatic enzymes for digesting proteins.

    • Trypsinogen, chymotrypsinogen, and procarboxypeptidase are the inactive forms of the proteolytic digestive enzymes.

    • Enteropeptidase, an enzyme secreted by the intestinal mucosa, activates trypsinogen.

    • Trypsin and chymotrypsin activate carboxypeptidase.

    • Trypsin, chymotrypsin, and carboxypeptidase split whole and partially digested proteins into peptides of various sizes without causing release of individual amino acids.

    • Carboxypeptidase and carboxyl esterase split some peptides into individual amino acids.

    • Trypsin inhibitor, a substance secreted by the pancreatic cells, prevents digestion of the pancreas itself.

    • In case of obstruction or other causes, the accumulation of enzymes in the pancreas can lead to autoactivation and acute pancreatitis.

    • The total secretion is greater when all stimuli of pancreatic secretion occur at once.

    • The pancreas releases secretions in response to multiple stimuli, which "multiply" or "potentiate" each other.

    • Vagus nerve stimulation: increases enzyme secretion and relaxes the sphincter of Oddi.

    • Secretin: released when acid chyme (stomach content) enters the duodenum, stimulates secretion of large quantities of H2O and NaHCO3 solution from ductal cells.

    • CCK: released in response to food in the small intestine, stimulates secretion of large quantities of H2O and NaHCO3 solution and pancreatic digestive enzymes.

    • Acetylcholine: released from vagus nerve endings and other cholinergic nerves in the enteric nervous system, stimulates enzyme secretion and relaxes the sphincter of Oddi.

    • Secretin and CCK act on different cells in the pancreas: secretin stimulates ductal cells to release a HCO3-rich fluid, while CCK stimulates acinar cells to release digestive enzymes.

    • The secreted HCO3- concentration is much higher than normal but has a low concentration of Cl-. H2CO3 formed from this reaction releases CO2 and H2O.

    • Secretin and CCK enhance each other's effects, leading to a greater total secretion than the sum of the secretions caused by each stimulus separately.

    • Trypsin inhibitors get degraded in the duodenum to allow trypsin to function.

    • Secretin is present in an inactive form (prosecretin) and has various effects on the pancreas and digestive system.

    • Acinar cells secrete a protein-rich (digestive enzymes) secretion in an isotonic plasma-like fluid, and ductal cells secrete a HCO3-rich fluid to alkalinize and hydrate it.

    • The main pancreatic duct joins the common bile duct and both open in the 2nd portion of the duodenum through the papilla of Vater.

    • The sphincter of Oddi is regulated by CCK, which can relax it to allow secretions to flow into the duodenum or squeeze the bile and pancreatic ducts to release components into the duodenal lumen.

    • Pancreatic secretions have major functions including neutralizing acid in the duodenal chyme, preventing damage to the duodenal mucosa, and providing an optimal pH for action of intestinal enzymes.

    • All gastrointestinal secretions are isosmotic except for saliva, which is hypoosmotic.

    • Enteropeptidase is a brush border enzyme and is not found in the pancreatic tissue or duct.

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    Description

    Test your knowledge of the phases of pancreatic secretions with this quiz. Learn about the cephalic, gastric, and intestinal phases and the stimuli and mediators involved in each phase.

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