Where do you find the Kupffer cells?
In the sinusoidal area of the liver (they act as resident macrophages)
Main function of lipocytes (aka ito cells or stellate cells)?
Store lipids
Tay-Sachs disease (sphingolipidosis)
Absence of b-hexosaminidase A (degrades acidic fatty gangliosides)
Metachromatic leukodystrophy (sulfatidosis)
Absence of aryisulfatase causes accumulation of sulfated cerebrosides
Type II glycogenosis
Acid maltase (acid alpha-glucosidase) is absent
Smooth ER function related to thyroid/metabolism?
dehaloginase converts T4 to T3 (thyroid hormone)
“A problem in the liver would also cause a problem with the thyroid”
Most important function of hepatocyte smooth ER?
biotransformation of drugs, metabolites and xenobiotics:
to detoxify and/or render water soluble
must conjugate/oxidize lipid-soluble molecules
What vitamins are stored in the liver and which vitamin is activated by the liver?
Vitamin A is stored in Ito cells; Vitamin K is also stored
Vitamin D is activated
Bile production begins where?
Hepatocytes
Which organ of the GI tract does NOT have a submucosa?
The gallbladder
Function of secretin?
induces biliary bicarbonate and H20 secretion
secretory stimulus from gut enteroendocrine cell
Function of cholecystokinin (CCK)?
induces gallbladder contraction and relaxes sphincter of Oddi
(secretory stimulus from gut enteroendocrine cell)
Trace the flow of bile from the hepatocytes to the gut:
Hepatocytes –> bile canaliculus –> bile duct (periphery of lobule) –> common bile duct –> duodenum
Where does the formation of secondary bile acids occur?
In the distal ileum and entire colon (Action of bacteria in terminal ileum and colon may dehydroxylate bile acids, yielding the secondary bile acids deoxycholic acid and lithocholic acid)
How much bile is produced/secreted per day?
1000 ml/day
How much bile can the gallbladder hold at once (approximately)?
50 ml/day of concentrated bile
Rough composition of bile?
~ 67% bile acid
~ 22% phospholipids
~ 4.0% cholesterol, 0.3% bilirubin, and 4.5% of protein
Details on the composition of bile
- Bile Salts (cholates, chenodeoxycholate, deoxycholate): produced by hepatic metabolism of cholesterol and excreted into bile.
Bile salts in bile act as detergents to dissolve dietary fat for absorption
Disruption bile excretion disrupts fat absorption & causes malabsorption
Patients develop diarrhea because of the resultant steatorrhea and then develop associated deficiencies of fat-soluble vitamins (A, D, E, & K) - Cholesterol and phospholipids: Only 4% of bile is cholesterol. However, hepatic secretion of cholesterol and its metabolites (bile salts) into bile is the body’s major route of cholesterol elimination.
Bile phospholipids enhance cholesterol solubilizing properties of bile salts
Inefficient excretion cholesterol can cause an increased serum cholesterol - Bilirubin: Comprises only 0.3% bile; responsible for bile’s green-black color.
Obstruction of bile flow leads to jaundice. - Protein and miscellaneous components: HCO3- (Bicarbonate)
Secretin, glucagon, VIP, and gastrin-releasing peptide (GRP) are all…
Choleretics
Somatostatin action?
Somatostatin either enhances fluid absorption or inhibits secretion
Where is the bile reabsorbed by active transport to get back to the liver?
The terminal ileum
The carrier state of Salmonella typhi is abolished by what surgical procedure?
Cholecystectomy
What sphincter exhibits the highest resting pressure?
The upper esophageal sphincter
Lower esophageal sphincter’s relaxation is caused by what two chemicals?
VIP and Nitric Oxide
