Pancreatic & Biliary Secretions Flashcards
What are the three parts of the small intestine?
Duodenum
Jejunum
Ileum
What does the small intestine receive?
chyme
pancreatic juice
bile
What structures make the small intestine ideal for absorption?
circular folds
villi
microvilli
What does the duodenum secrete into the blood?
Gastrin - D cells CCK - I cells - duodenum and jejunum Secretin - S cells - duodenum Motilin - M cells - duodenum and jejunum Glucose-dependent Insulinotropic peptide - K cells of duodenum and jujenum
How much does the duodenum secrete a day?
2L
What are the enhancing control mechanisms for secretion?
distension, irritation, gastrin and CCK, secretin and parasympathetic activity
What is the inhibitory control mechanism for secretion?
sympathetic nerve activity
What does the secretions from the small intestine contain?
mucus
aqueous salt
no digestive enzymes
What transporters are involved in secretion?
Na-K ATPase - apical, NKCC - apical, CFTR - basolateral
What happens during segmentation?
chopping movements move chyme back and forth vigorously with alternating contractions and relaxations of segments of the circular muscle
What is the frequency of segmentation in the sm. intestine?
duodenum has 12/min, ileum has 9/min which moved food along
What is the gastroileal reflex?
where segmentation occurs in the empty ileum due to gastrin
What peristalic activities occur in the fasting state?
a few localised contractions
the migrating motor complex
What is the migrating motor complex?
occurs between meals 90-120mins
strong peristalic contractions passing length of small intestine
clears sm. intestine of undigested debris, mucus and sloughed epithelial cells
What triggers the migrating motor complex?
motilin
what inhibits the migrating motor complex?
feeding and vagal activity
gastrin and CCK
Where do the digestive enzymes from the pancreas come from?
acinar cells
What does the pancreas secrete for digestion?
aqeous NaHCO3 from duct cells
digestive enzymes from the acinar cells
What pancreatic enzymes are produced by the acinar cells?
trypsinogen chymotrypsinogen procarboxypeptidase pancreatic amylase pancreatic lipase
What activates trypsinogen in the first instance?
enterkinase
where is enterokinase made?
the mucosal cells
What is the function of the aqeuos NaHCO3 secretion from the duct cells?
neutralises acid chyme
ideal pH for enzymes
protects mucosa from erosion by acid
CF patients have reduced secretion
What are the three phases of pancreatic secretion?
cephalic
gastric
intestinal
What occurs in the cephalic phase of pancreatic secretion?
increase vagal stimulation of acinar cells
What occurs in the gastric phase of pancreatic secretion?
distension -> vagovagal reflex resulting in parasympathetic stimulation of acinar and duct cells
What occurs in the intestinal phase of pancreatic secretion?
increased acid -> increased secretin -> increases NaHC03 from duct cells
increased fat/protein in duodenum -> increased CCK -> increases enzymes from acinar cells
What are the hepatic ducts?
left, right, common
What are the bile ducts?
cystic, common
Where do the secretions from the gall bladder, liver and pancrease all meet?
sphincter of oddi
how much bile is produced daily?
0.6-1.2L
Where is bile stored between meals?
in the gall bladder
What happens to bile during a meal?
chyme in the duodenum stimulates gall bladder sm. muscle to contract via CCK and vagal impulses
What causes the sphincter of Oddi to open ?
CCK
What two cells secrete bile?
hepatocytes
cholangiocytes
What does bile specifically aid in the digestion of?
fats
what increases the flow rate of bile?
secretin
what does the bile contribute to?
micelle formation
neutralisation of chyme
pH adjustment for enzymes
protection of the mucosa
what is hepatic bile composed of?
primary bile acids forming bile salts with Na and K cholic acid chenodeoxycholic acid water and electrolytes cholesterol lipids and phospholipids IgA Bilirubin
What are bile salts usually conjugated with?
glycine or taurine - occasionally sulfate
Why is only a small amount of bile produced in relation to the amount released?
it is recycled enterohepatically from the gut
What resins bind bile salts to lower cholesterol?
colestryamine
colestipol
How is bile synthesis regulated?
dependent on hepatic blood concentration of salts
low stimulates production
How is bile secretion regulated?
Bile salt returning to liver stimulates secretion
CCK
Secretin
Vagal Activity
What is secretin released in response to?
acid in the lumen of the gut
What does secretin stimulate?
Increased NaHCO3 secretion from pancreatic duct cells and hepatobiliary cells
decreased gastric secretion and emptying
What is CCK released in response to?
fat and protein in the duodenal lumen
What does CCK stimulate?
increased digestive enzymes from acinar cells
contracts gallbladder and relaxes sphincter of oddi
decreased gastric secretion and emptying
What drugs might you use in analgesia for GI?
morphine, bupenorphine, pethidine
What drugs might you use to ease biliary spasm?
atropine, GTN
