Lecture 40 11/27/23 Flashcards
Which functions of hormones/secretions in the duodenum and jejunum are associated with providing time for present food to process?
-decreased appetite
-inhibition of gastric acid secretion
-slowing of gastric emptying
Which functions of hormones/secretions in the duodenum and jejunum are associated with optimizing digestion?
-releasing bicarbonate to neutralize acidic chyme
-stimulating digestive enzyme secretion
-stimulating bile acid secretion
What are the stimuli for secretin production?
-low duodenal pH
-intraduodenal nutrients
What are the actions of secretin?
-inhibit acid secretion
-slow gastric emptying
-stimulate HCO3-rich pancreatic fluid secretion
Which enzyme is involved in sodium-bicarbonate buffering of hydrochloric acid?
carbonic anhydrase
What are the stimuli for cholecystokinin (CCK)?
-intraduodenal nutrients
-H+ ions
What are the actions of CCK?
-inhibit gastric emptying
-increase secretin secretion
-increase pancreatic enzyme secretion
-stimulate pancreatic growth
-cause gall bladder to contract
-relax sphincter of Oddi in the gall bladder
What is the stimulus of gastric inhibitory peptide?
intraduodenal nutrients
What are the actions of gastric inhibitory peptide?
-inhibition of gastric acid secretion
-stimulation of pancreatic insulin release when blood sugar is high (incretin)
What is an incretin?
a substance that increases insulin release
Which type of pancreas makes up the majority of the pancreas?
exocrine
How is the exocrine pancreas arranged?
into acini and ducts
What are the characteristics of pancreatic enzyme secretion?
-secreted by acinar cells
-stimulated by CCK and acetylcholine
What are the characteristics of bicarbonate-rich fluid secretion?
-secreted by ductal cells
-stimulated by secretin
What are zymogens?
the precursor molecules of protein-digesting enzymes
Why are protein-digesting enzymes produced as zymogens first, instead of in their active form?
active form could break down pancreatic tissue
Where are zymogens activated into protein-digesting enzymes?
duodenal lumen
What are the characteristics of trypsinogen?
-activated into trypsin
-activated by enterokinase
-trypsin activates the other protein-digesting enzymes
Which zymogens are activated by trypsin?
-chymotrypsinogen -> chymotrypsin
-procarboxypolypeptidase -> carboxypolypeptidase
What are the characteristics of trypsin inhibitor?
-secreted by glandular cells of the pancreas
-prevent premature activation of trypsin
What is amylase?
the carbohydrate-digesting enzyme
Which form of amylase is the main enzyme for starch digestion?
pancreatic amylase
What are the three fat-digesting enzymes?
-pancreatic lipase
-cholesterol esterase
-phospholipase
What are the characteristics of sodium-bicarbonate?
-produced by pancreatic ductal cells
-secretion stimulated by secretin
What are the functions of sodium-bicarbonate?
-buffer gastric acid coming from the stomach
-provide volume to carry digestive enzymes from pancreatic acini
Which hormone/secretion is the main trigger for enzyme release?
CCK
What are the regulatory characteristics of acetylcholine?
-released from parasympathetic vagus nerve
-stimulates acinar cells to release enzymes
What are the regulatory characteristics of CCK?
-secreted from duodenum/jejunum
-stimulated by intraduodenal nutrients
-stimulates acinar cells to release enzymes
What are the regulatory characteristics of secretin?
-secreted from duodenum/jejunum
-stimulated by low duodenal pH
-stimulate pancreatic duct cells to release water and sodium-bicarbonate
Which phase of secretion sees the most pancreatic secretion occuring?
intestinal phase
What are the characteristics of bile?
-secreted by hepatocytes into canaliculi
-flows progressively into larger ducts until reaching hepatic and common bile ducts
-can enter duodenum or be stored in gall bladder
What does bile consist of?
-bile salts
-pigments
-cholesterol
-phospholipids
-electrolytes
-bicarbonate
What are the functions of bile?
-fat digestion and absorption
-removal of waste products
Which secretion triggers the release of bile?
CCK
What are the characteristics of bile acids?
-steroid acids formed from cholesterol
-act as detergents and make lipids soluble in water
What are the characteristics of bile salts?
-conjugated bile acids
-conjugated to amino acids (glycine or taurine)
What is the main characteristic of primary bile acids?
produced by the liver
What are examples of primary bile acids?
-cholic acid
-chenodeoxycholic acid
What are the characteristics of secondary bile acids?
-have been deconjugated and dehydroxylated
-formed by action of bacteria on bile salts in the intestines
What are examples of secondary bile acids?
-deoxycholic acid
-lithocholic acid
What are the characteristics of bile acid recovery?
-majority of bile acids are recirculated
-reabsorbed in ileum
-enter portal system and go to liver
-liver recovers and conjugates bile acids
What are the characteristics of emulsification?
-breaks large fat particles into small particles
-provides larger surface area for lipase enzymes to attack
What are the steps of making lipids water soluble?
-bile salts combine with dietary fats to form micelles
-micelle formation allows dietary fats to cross aqueous layer to enter enterocytes
What is the stimulus for peptide YY?
detection of material within distal intestines and colon
What are the actions of peptide YY?
-signals satiety
-inhibits gastric emptying
