Bile Gall Bladder And Gall Stones Flashcards
What is Physiology and functions of the gallbladder
Storage and concentration of bile • Concentrated because of active Na + transport (and H 2O) from gallbladder Hepatic Gallbladder bile duct bile % of solids 2-4 10-12 pH 7.8-8.6 7.0-7.4 • The pH of bile drops (becomes “acidic”) as Na+ is exchanged for H + • Pancreatic juice: bile salts, bile pigments and dissolved substances in alkaline electrolytes
What is bile made from
Bile → larger ductules and ducts (composition is modified) • Water is (may be) added via specific tight junctions within ductules (
cholangiocytes)
• The ductules scavenge glucose, amino acids; GSH is hydrolysed • Ductules secrete IgA ( mucosal protection), HCO3- and H 2O in response to
secretin in the postprandial period
How does bile flow
Bile flows as follows:
Hepatocytes ↓ Bile canaliculi (merge to form ductules) ↓ Terminal bile ducts ↓ Hepatic ducts (left and right) ↓ Common bile duct
What are the two cell types that secrete bile
Hepatocytes: cholesterol, lecithin, bile acids, bile
pigments (bilirubin, biliverdin, urobilin, etc.) 2. Epithelial cells of bile ducts : bicarbonate-rich salt
solution
– Secretin & ACh influence the secretion of
bicarbonate-rich salt solutions and H 2O
When is secretion of bile the greatest
Secretion of bile is greatest during and after a meal
• Increased [bile salt] blood → ↑ bile salt synthesis & secretion into bile canaliculi …..> gallbladder
Increased secretion →↑flow of bile
What substances are secreted across the bile canalicular membrane?
Substances secreted across the bile canalicular membrane: • Bile acids • Phosphatidylcholine • Conjugated bilirubin • Cholesterol • Xenobiotics (foreign chemicals/substances, e.g. drugs)
– Specific transporters ferry the above into bile
– Substances such as water, glucose, Ca 2+, GSH, amino acids and urea
enter the bile by diffusion
Compare hepatic bile vs gallbladder bile
Hepatic bile = 97% water; cholesterol, lecithin, bile acids, bile pigments,
etc.
• Gallbladder bile: 89% water; HCO3-, Cl -, Ca 2+, Mg2+, Na+, cholesterol,
bilirubin, bile salts, etc.
– Bile concentrated in gallbladder (NaCl and H 2O loss → increased solid
content)
– Bile goes to the gallbladder between meals when sphincter of Oddi is
closed
What are bile acids/salts
Bile acids are important in GI • Made from cholesterol – helps to reduce cholesterol levels • Secreted into bile and conjugated to glycine or taurine
• Conjugation helps to increase the ability of bile acids to be secreted and
also decreases their cytotoxicity
• Bile acids are also called bile salts
What are the 4 major bile acids found in humans:
Cholic acid: 50% = quantitatively more important • - primary*Chenodeoxycholic acid: 30%- primary bile -liver
• $Deoxycholic acid: 15% - secondary bile
• $Lithocholic acid: 5%-secondary bile
Primary set - firmed in liver
Secondary formed in colon
What are the main functions of bile : metabolic regulators
Elimination of cholesterol to bile acids ( 5% excreted in faeces )
– Synthesis and subsequent excretion of bile acids in the faeces
represents a significant mechanism for the elimination of excess cholesterol
2. Reduce the precipitation of cholesterol in gallbladder; bile acids and
phospholipids help solubilise cholesterol in the bile 3. Facilitate the absorption of fat-soluble vitamins (ADEK) 4. Regulate their own transport and metabolism via enterohepatic
circulation 5. Facilitate the digestion of triglycerides - work in concert with
phospholipids (licithin) and monoglycerides to ensure the emulsification
of fats
Describe process fir gall bladder emptying
Cephalic phase: taste, smell and presence of food in the mouth →
impulses via vagus nerve • Gastric phase: distension of stomach generates impulses in vagus nerve • Intestinal phase: period of most gallbladder emptying; key mediators for
the increased release are
Cck and secretion
What dues cck and acetylcholine do
Cyst muscle contracting
What is the effect if motilin
Motilin → gallbladder motility and ↑ volume of gall bladder secretions
