Physiology/pharmacology of liver Flashcards
what are the metabolic functions of the liver?
regulation of carbohydrate, lipid and amino acid metabolism
describe the processes in carbohydrate metabolism
hormonally regulated
gluconeogenesis (glucose from amino acids)
glycolysis (form pyruvate/lactate/acetyl CoA)
glycogenesis (store glucose as glycogen)
glycogenolysis (release glucose as needed)
what are the processes in fat metabolism?
processing of chylomicron remnants
synthesis of lipoproteins (VLDLs, HDLs) and cholesterol (for steroid hormone/bile synthesis)
Ketogenesis (temp energy source in starvation) - important for neural function
what are the processes in protein metabolism?
synthesis of plasma proteins
transamination and deamination of amino acids
conversion of ammonia to urea (urea cycle - detoxify)
what is the role of the liver in hormone metabolism?
inactivates/degrades many hormones and activates others
what hormones does the liver deactivate?
insulin
glucagon
ADH/vasopressin
steroid hormone
what hormones does the liver activate?
conversion of thyroid hormone (TH) by deiodini.
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what substances are stored in the liver?
fat soluble vitamins (A (in Ito cells), D, E, K (in hepatocytes))
Vit B12 (long term - 3-5 years)
Iron, copper
Glycogen
what is involved in the liver’s synthesis of proteins?
for export:
- coagulation factors II, VII, IX and X and proteins C and S
- albumin
- complement proteins
- apolipoproteins
- carrier proteins (secreted into blood and carries other substances eg. thyroid hormone)
what are Kupffer cells?
like resident macrophages
liver phagocytes that digest/destroy particulate matter (eg bacteria) and senescent (old) erythrocytes
How is the liver involved in protection?
Kupffer cells
production of immune factors
- host defence proteins (acute phase proteins)
how is the liver involved in detoxification?
detoxifies many…
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what does bile do?
participates in digestion and absorption of fats and the excretion products of metabolism (including drug metabolites)
how is bile produced?
0.6-1.2L per day by combined secretion from hepatocytes and bile duct cells (cholangiocytes)
where happens to bile between meals?
stored and concentrated (removes bile and water) in the gall bladder (sphincter of oddi closed)
what are the risks of concentrating bile?
components can precipitate out (e.g cholesterol) triggering formation of gall stones
what happens to bile during a meal?
chime in duodenum stimulaes gall bladder smooth muscle to contract and sphincter of oddi to open (via CCK and vagal impulses)
Bile spurts into duodenum via cystic and common bile ducts and mixes with bile from liver
what are the functions of bile?
micelles formation
neutralization of chime
pH adjustment for digestive enzyme action
protection of mucosa
how do hepatocytes secrete primary juice?
secrete juice into canaliculi which drain into biliary ductules and ducts
materials removed from sinusoidal capillary into space of disse, across a membrane?
what blood is in the sinusoidal capillaries?
hepatic portal vein and hepatic artery blood
what is contained in secretion from hepatocytes?
primary bile acids, mainly cholic and chenodeoxycholic acids (a fraction of which are dehydroxylated by bacteria in the gut to form the secondary bile acids, deoxycholic acid and lithocholic acids)
Both the primary and secondary acids are then absorbed and taken back via the hepatic portal vein and can be reused and resecreted into the duodenum
Water and electrolytes (incuding Na, K, Cl, Ca2+ and HCO3)
Lipids and phospholipids
Cholesterol
IgA
Billirubin (renders urine yellow and faeces brown)
Metabolic waste and drug metabolites
what is cholelithiasis?
excess cholesterol relative to bile acids and lecithin may precipitate into microcrystals that aggregate into gall stones
what does dark urine and pale stool indicate?
bilirubin problem
what is the most common pathology of the biliary tract?
cholelithiasis
