Liver Flashcards
where does the falciform ligament attach the liver to
anterior abdominal wall
what does the falciform ligament contain
ligamentum teres
what is the ligamentum teres a remnant of
umbilical vein
what are the liver impressions (6)
oesophageal renal colic duodenal gastric gallbladder
what is the dominant blood supply to the liver
portal system
venous drainage from GI tract to liver via hepatic portal vein
what is the structural and functional unit of liver
structural - lobules
functional - acinus
what is a liver lobule
hexagonal shape with central vein
where does the portal triad lie in the lobule
at the corners
what is the portal triad
hepatic artery
hepatic portal vein
bile duct
what is an acinus
functional liver unit
localised collection of hepatocytes around portal triad
what are sinusoids
discontinuous capillary
- mixes oxygenated blood from hepatic artery w nutrient rich blood from hepatic portal vein
what is the gallbladder
peritoneal structure involved w storage and bile conc
where does the common bile duct empty into the duodenum
major duodenal papilla (controlled by sphincter of Oddi)
what are the fat soluble vitamims
A
D
E
K
discuss vit A
retinal light adaptation
what is vit A found in
carrots
discuss vit D
increase intestinal calcium uptake
what is vit D found in
milk
discuss vit E
prevents RBC destruction
what is vit E found in
veg oil
discuss vit K
normal blood clotting
what is vit K found in
spinach
how is vit A metabolised (5)
- retinol absorbed by enterocytes
- retinol is esterified and incorporated into chylomicrons
- chylomicrons travel through intestinal lymph to liver
- retinol de-esterified and bound to retinol binding protein
- retinol stored in lipid droplets of sinusoidal pericytes
what is vit A aka
retinol
what is vit B aka
folate
how is vit B metabolised (5)
- vit B binds to R protein released from salivary glands n stomach (protects vit B from HCl
- pancreatic proteases free vit B in duodenum
- vit B binds to intrinsic factors (released from parietal cells)
- vit B-IF complex absorbed in enterocytes of terminal ileum
- vit B transported in blood to liver, then back to duodenum in bile (enterohepatic circulation)
how is vit D metabolised
- D3 (synthesised from liver) transported to liver n converted to calcidiol (25hydroxyvitaminD)
- intermediate travels to kidney and converted to calcitriol (1,25dihydroxyvitaminD)
- calcitriol binds to vit D receptors in target tissues
how is iron metabolised (5)
- iron is absorbed into enterocytes
- some iron is bound in enterocytic ferritin, rest transported to blood via ferroportin
- iron in blood bound to transferrin travels to liver
- transferrin in hepatocytes n kupffer cells stores iron in ferritin
- when hepatic iron stores are full, hepatocytes release hepcidin which inhibits ferroportin iron transport across enterocyte basolateral membrane
what is calcidiol
25 hydroxy vitamin D
what is calcitriol
1,25dihydroxy vitamin D
what are xenobiotics
foreign substances that are absorbed (skin, lungs, intestine) and are not used for energy purpose
what does phase 1 reaction involve
microsomal enzymes found in smooth ER
what does phase 2 reaction involve
non-microsomal enzymes found in cytosol
which enzyme is involved in phase 1 reactions
cytochrome p450
what happens during phase 1
oxidation
hydrolysis
small hydrophilicity increase
what happens during phase 2
glucoronidation - greatly increases hydrophilicity
what does hydrophilicity result in
water soluble = able to excrete
what is glucuronidation
conjugation of substance with glucuronic acid
where is albumin produced
hepatocytes
list 3 functions of albumin
- maintains oncotic pressure (fluid distribution)
- acts as a carrier for hormones and molecules
- mops up free radicals
how do complement factors enhance immune system
by stimulating cytokine release
what are the 2 types of protein degradation
lysosomal
non-lysosomal
describe lysosomal protein degradation
kupffer cells phagocytose unnecessary proteins
describe non-lysosomal protein degradation
ubiquitin binds to protein for destruction
proteasome encases protein and destroys (aa can be recycled)
what are the 3 steps of the glucose/alanine cycle
- alanine aminotransferase removes amine from glutamate and adds it to pyruvate to form alanine (transamination) and an alpha keto acid (used in Krebs)
- alanine is transported in blood to liver and broken down into pyruvate and an ammonia group
- pyruvate is used for gluconeogenesis, an the ammonia group is incorporated into the urea cycle
what removes Amine from glutamate n adds it to pyruvate to form alanine n alpha keto acid (and what is this called)
alanine aminotransferase
- transamination
where is the alpha keto acid from transamination used
krebs
where is alanine transported to, where it is broken down
liver
when alanine is broken down in the liver, what is broken into
pyruvate - used in gluconeogeesis
ammonia group - incorporated in urea cycle
what are the functions of the glucose alanine cycle (2)
- provides liver w necessary ingredients for gluconeogenesis and urea cycle
- muscles don’t have to use energy to make glucose - all energy can go to muscle contraction
what are the 4 steps of the urea cycle
- ammonia n carbon dioxide –> carbomyl phosphate
- carbomyl phosphate + ornithine –> citrulline
- citrulline –> arginine & another ammonia group added
- arginine cleaved by arginase –> urea and ornithine
how many ATP does the urea cycle require
3
how many ammonia molecules are secreted during urea cycle
2
where are chylomicrons synthesised
enterocytes
where are VLDL’s synthesised
hepatocytes
what is the function of chylomicrons/VLDL
transport of triglycerides from liver to tissues
what does lipoprotein lipase do to VLDL
strips triglyceride from VLDL
degrades the to glycerol and 3 fatty acids
what are chylomicrons
lipoprotein particles that consist of triglycerides, phospholipids, cholesterol, and proteins
what is the diff btwn VLDL and chylomicrons
VLDL transports endogenous products, whereas chylomicrons transport exogenous (dietary) products
what is LDL produced by
hepatic lipase in hepatocytes
what do LDL do
transport cholesterol from liver to tissue cell membranes (taken up by endocytosis)
what does HDL do
removes excess cholesterol from cells and returns to liver
what happens to excess cholesterol (HDL)
converted into bile salts n excreted
or involved in fat emulsification
what happens during beta oxidation
- fatty acids diffuse across cell membranes
- fatty acid combine with coenzyme A to form acyl coenzyme A (catalyst by acyl CoA synthase)
- acyl coA transported across mitochondrial membrane via cartinine shuttle
- beta oxidation - 2 carbons are removed from fatty acid –> acetyl CoA, NADH and FADH (krebs/oxidative phosphorylation)
what does high levels of fatty acid oxidation result in
excess acetyl CoA (too much for Krebs) –> increased ketogenesis
what are the 3 products of hepatic lipid metabolism
acetoacetate (converted immediately to acetone)
acetone
hydroxybutyrate
how is fatty acid oxidation regulated
high concentration of glycerol-3-phosphate = high levels of fatty acid oxidation
- insulin inhibits fatty acid oxidation
- glucagon activates fatty acid oxidation
how does insulin affect fatty acid oxidation
inhibits
how does glucagon affect fatty acid oxidation
activates
what is ketoacidosis
diabetic - low insulin
alcoholic - high glucagon
ketones = strong acids –> lower blood pH –> oxygen can’t bind to Hb effectively
what is insulin like in a diabetic
low
what is glucagon like in an alcoholic
high
how do ketones impact pH
lower
what are bile salts
primarily cholesterol n waste products that need to be excreted
where is bile produced
hepatocytes
what is bile transported in
miceles
bile is transported in micelles through what?
canaliculi
why is bile transported in canaliculi
bc bile damages cell membranes
what helps bile move to hepatic ducts
actin filaments that contract around canaliculi
what is the path of bile to the gallbladder
liver - canaliculi - hepatic ducts - cystic duct - gallbladder (Sphincter of odd closed)
how is bile released (4)
- food enters duodenum, CCK released
- gallbladder contracts and sphincter of Oddi opens
- bile enters the duodenum and emulsifies fats
- bile salts are reabsorbed in the terminal ileum - enterohepatic circulation
how is bilirubin metabolised (6)
- kupffer cells break down haem to biliverdin
- biliverdin converted to bilirubin (catalysed by biliverdin reductase)
- bilirubin released from kupffer cells and travels in blood bound to albumin
- hepatocytes conjugate bilirubin with glucuronic acid (catalysed by glucuronyl transferase)
- water soluble conjugated bilirubin is excreted in bile and unconjugated in duodenum
- majority of bilirubin secreted as stercobilin (makes poo brown) or urobilin (makes pee yellow), some is recycled via enterohepatic circulation
what breaks down haem to biliverdin
kupffer cells
which enzyme catalyses biliverdin –> bilirubin
biliverdin reductase
when bilirubin is conjugated with glucuronic acid, which enzyme catalyses it
glucuronyl transferase
