bile, gall bladdder, gallstones Flashcards
primary function of gallbladder
concentration and storage of bile
how does the gallbladder concentrate bile
active na+ transport from gallbladder is followed actively by water
how does bile in the GB become acidic
Na+ exchanged for protons
how does {Na+] increase in bile stroage
more Cl- and HCO3- are lost
what makes up pancreatic juice
bile salts, pigments, dissolved substances in alkaline electrolytes
which substances are secreted across the bile canalicular membrane
bile acids phosphatidylcholine (PC) conjugated bilirubin cholesterol xenobiotics
how do water, glucose, GSH, AA, urea etc enter the bile
diffusion
what is the correct ratio of bile acids:phosphatidylcholine:cholesterol in canalicular bile
10:3:1
what happens if the normal acid ratio for acid:PC:cholesterol is altered
formation of cholesterol gallstones
where is the bile modified
larger ductules and ducts
how is bile composition modified
water may be added by specific junctions w/in the ductules
- ductules scavenge glu, AA, - GSH is hydrolysed
why do ductules secrete IgA
mucosal protection
why do ductules secrete HCO3-
response to secretin in the postprandial period
what are bile salts made of
bile + cation e.g. Na+
what are the four main human bile acids
cholic acid
chenodeoxycholic acid
deoxycholic acid
lithocholic acid
what happens to bile acids when they reach the intestine
deconjugated by bacteria, then excreted or reabsorbed
how are bile acids removed by the intestine
by portal circulation into the liver
what do anaerobic bacteria in the colon do to 1* bile acids
modify them to 2* bile acids e.g cholic > deoxycholic acid
chenodeoxycholic acid > lithocholic acid
what are bile acids made from
cholesterol
what happens to bile acids before they’re secreted into bile
conjugated to glycine or tauring
what does conjugation do
increase the ability of bile acids to be secreted, decreases their cytotoxicity
metabolic functions of bile acids
reduce precipitation of cholesterol in the gall bladder
allow fat digestion via emulsification
allow fat soluble vitamins to be absorbed
regulate lipid and glucose metabolism
what makes up hepatic bile
97% water
cholesterol
lecithin
bile acids, pigments
what makes up gallbladder bile
89% water bicarb Cl- Ca2+ mg, na, cholesterol, bilirubin
which 2 types of cells secrete bile
hepatocytes, epithelial cells of bile ducts
what does secretin do
influences secretion of bicarb-rich salt solutions and water
when is bile secretion greatest
during and after eating
what does the sphincter of Oddi do during fasting periods
contracts - no communication between duodenum and pancreas
when does the sphincter of Oddi relax
during and after meals
how is contraction of the gallbladder controlled
impulses via vagus nerve - gastric phase (stomach distension) and cephalic phase
what is the intestinal phase
- period of most gallbladder emptying - CCK and secretin
what does motilin modulate
gallbladder motility and volume
what stimulates secretion of cholecystokinin (CCK)
presence of fatty meal
what is stimulated by a rise in plasma CCK
gallbladder contraction
relaxation of sphincter of Oddi
what is caused by gallbladder contraction
increased bile flow into Common bile duct
what does increased flow into CBD and relaxation of sphincter of Oddi cause
increased flow of bile into duodenum
where are bile salts and lecithin synthesized
liver
where do HCO3- and other ions act
duodenum - synthesise acids
how are bile salts related to GI function
really fucking important
what reabsorbs bile salts
Na+/bile salt coupled transporters
how do bile salts get recycled
returned to liver and secreted back into the bile
what is the recycling pathway from intestine to liver to intestine called
enterohepatic circulation
how often can the contents of the body’s bile acid pool get recylced
up to twice per meal
what ultimately happens to the cholesterol in bile
excreted in the faeces
what can interruption of the enterohepatic circulation cause
excess synthesis of bile salts by liver
excretion by the kidneys of bile salts, plus some cholesterol
fancy name for gallstones
cholelithiasis
gender ratio of incidence of gallstones
2:1 (F:M)
what happens to concentration of phospholipids and bile salts in bile if the cholesterol content is increased
the phospholipid and bile salt concentration is increased
how does cholesterol form gallstones
crystallization, precipitation of bile pigments
what are the 2 types of gallstones
calcium bilirubinate
cholesterol
factors in formation of gallstones
bile stasis - sequesteration in gallbladder
decreased amount of bile acids due to malabsorption
chronic infection
supersaturation of bile with cholesterol
why is bile yellow
bilirubin
where do larger gallstones lodge
opening of the gallbladder
what happens if gallstones lodge at the point where the bile duct joins the duodenum
stoppage of bile and pancreatic secretions
what is jaundice
increased accumulation of bilirubin in the blood caused by pressure build up causing decreased bile secretion
how are gallstones diagnosed
ultrasound/CT in upper right quadrant of gallbaldder
clinical features of gallstones
if neck of cystic duct is impaired, there will be biliary pain
common bile duct - bile flow obstruction - cholestatic jaundice which can cause infection
