Pancreas & Biliary System Flashcards
describe anatomical components of pancreas, function
located right below stomach:
- pancreatic duct/common bile duct/ ampulla of Vater
- sphincter of hepatopancreatic ampulla/sphincter of Oddi
- pancreatic exocrine secretions produced by cells in pancreatic acini
- acinar cells line terminal end acinus, secrete digestive enzymes
- duct cells line neck of acinus, secrete alkaline fluid
identify pancreatic secretions, discuss function and control mechanisms
Pancreas supplies enzymes that breakdown proteins, carbs, fats and alkaline fluid to the small intestine to neutralize chyme. 3 enzymes that breakdown protein:
- trypsinogen (cleaved by enterokinase). then trypsin activates others
- chymotrypsinogen
- procarboxypeptidase
have potential for auto-digestion, stored inactivated in zymogen granules.
also produces trypsin inhibitor
- pancreatic amylase- secreted in active form
- pancreatic lipase- *** only enzyme that can digest fat
aqueous alkaline secretion- pancreatic enzymes require neutral pH, duodenum can’t handle acid
CONTROL
- PSNS input increases all
- SNS decreases all
- hormonal influences dominate
- secretin, released in presence of chyme in duo by mucosal cells, increase NaHCO3 release from pancreas
- CCK released in presence fat in duo by mucosal cells, stimulates production/release lipase and proteolytic enzymes
liver: describe anatomical and functional organization
hepatocytes produce bile salts, store in gall bladder, secreted into duo via common bile duct
liver organized into hepatic lobule-
- hexagonal arrangement around central vein
- at each corner there is branch of artery, vein, bile duct
- each hepatocyte borders a sinusoid, and a bile canaliculi
hepatocytes continually secrete bile into canaliculi
liver: describe hepatic-portal circulation
2 distinct blood sources:
- venous blood from GI via hepatic portal vein
- arterial blood via hepatic artery
venous blood enters liver, breaks into liver sinusoids
hepatic portal system allows liver to process/detox substances absorbed in GI
liver has 1st pass option to take nutrients
sinusoids receive arterial blood
liver: outline enterohepatic circulation, function
bile delivered to duo via sphincter of Oddi
- in absence of duo chyme, sphincter closed
- bile goes to gall for storage
- majority bile salts reabsorbed in terminal ileum into portal vein, get recycled in liver
- 5% lost, provides method cholesterol regulation
liver secretions: detail components in bile, function in fat diggestion
- alkaline solution (duct cells)
- bile salts (hepatocytes)- deprotonated molecules, - charge, derived from cholesterol but - hydrophilic tail. breakdown size fat droplets
- bilirubin (hepatocytes)- yellow pigment from RBC degradation, derived from HG,
- lecithin (hepatocytes)- component of PM
BILE
- lipase only acts on surface of fat aggregates
- bile salts act as detergent, emulsify fat into small pieces. cholesterol portion of bile dissolves in fat. hydrophilic tail exposed to aqueous chyme repel other droplets
colipase anchors lipase to bile salts at surface
following lipase digestion, bile help form microdroplets of MG “micelles” composed of bile salts, cholesterol, lecithin which form hydrophobic core with hydrophilic shell, shuttle digested fat to epithelial surface
liver secretions: factors that stimulate bile production, how it stops
Release- hormonal/autonomic inputs regulate releae bile
- CCK triggers contraction gall bladder, relaxation Oddi
- Vagal efferent augment this (PSNS, CN10)
Production/secretion
- vagal input increased production
- secretin stimulate production NaHCO3, component of bile
bile salts
- in blood from reabsorption, most potent stimulator further production/release POSTIVE FB
INHIBTION
- when fats leave duodenum, CCK levels drop, Oddi closes, bile can’t enter duo
- hepatocytes keep making bile until circulating bile salts declines
