Functional Microanatomy of the Liver Flashcards
what provides gross support to the liver
the collagen of the branching vascular system
what supports parenchymal cells of the liver
fine reticular fibres
what does the portal vein carry
food rich blood from the gut
what supplies arterial blood to the liver
hepatic artery
function of hepatic veins
takes away processed blood into the vena cava
what percentage of the blood supply comes from the hepatic artery vs. portal vein
hepatic artery - 25%
portal vein - 75%
what is the nerve supply to the liver
sympathetic and parasympathetic nerves supply perivascular structures but there is very little nerve supply at the sinusoidal level
what direction and speed does blood flow through the liver lobule
from portal triad to central vein
moves slowly to allow exchange of oxygen and nutrients
width of central vein wall
very thin
where are sublobular veins found
alone at periphery of the lobule
what is found in the portal area
portal triad
describe blood flow in hepatic lobules
- starts from branches of the portal vein and hepatic artery
- flows towards central vein via sinusoids
- blood collected in central veins goes to sublobular veins
- then to collecting veins
- then hepatic veins which leave the liver
describe bile flow in the liver
moves from centre to the peripheral bile ducts within a cell plate in a bile canaliculi
what are the three zones of the acinus
- periportal
- intermediate
- perivenous
what are the functions of the periporatl, intermediate and perivenous regions of the liver acinus
periportal - deals with sampling of the blood
intermediate - changes blood composition
perivenous - enriches blood
are liver sinusoids low or high pressure channesl
low - so blood moves slowly and has time to be processed
what cell type lines the liver sinusoids
fenestrated endothelial cells
are fenestrated endothelial cells that line the liver loosely or tightly attached and what do they rest upon
loosely
microvilli of underlying hepatic cells
what is the function of kupffer cells
policemen - surveillence
look for intruders
phagocytose them
send signals to other cells for help
what is the space of diss
the space between the fenestrated epithlelial cells and the hepatocytes
does the space of diss have a basal lamina
no but does contain extracellular matric materials
what do stellate cells store
fat and vitamin A
how do stellate cells respond to insults
make collagen and cause cirrhosis
can RBCs enter the space of diss
no
what function does the sinusoidal wall have in the embryo
haematopoiesis
functions of sinusoidal wall
blood cleansing (e.g. of gut bacterial toxins)
bringing plasma in close contact with hepatocytes for its many functions
at are the functions of the hepatocytes
storage
transformations
synthesis
regulation of plasma concentrations
detoxification
production of bile
production of acute-phase proteins which assist defence
where is bile produced
hepatocytes
where are bile canaliculi found
between neighboring hepatocytes
which face of hepatocytes has microvilli in abundance
sinusoidal face
lateral faces which make the bile canaliculi don’t have many
what shape are hepatocyte nuclei and how many nucleoli are there
round
one or two
how many nuclei do hepatocytes have
mostly one but sometimes two
what is the cause of portal hypertension
stellate cells depositing collagen which makes it harder for blood to pass through fenestrated epithelial cells so pressure is increased to overcome this
how is lymph formed in the liver
by filtration of plasma into the spaces of disse
what route do lymphatics follow
same as portal vein
function of insulin
responds to high blood glucose
increases glycogen storage in liver
decreases gluconeogenesis
decreases glycogenolysis
increases glucose uptake
which decreases blood glucose
glucagon is the opposite
describe bilirubin metabolism
- haemolysis in blood vessels forms unconjugated bilirubin
- unconjugated bilirubin turned into conjugated bilirubin in the liver
- conjugated bilirubin passed through biliary system into small intestine
- bacterial proteases in small intestine turn conjugated bilirubin into urobilinogen
5a. 90% urobilinogen excrete in faeces
5b. 10% urobilinogen returned to liver by the portal vein - 10% urobilinogen returns to blood
- kidneys excrete 10% urobilinogen in urine
what percentage of urobilinogen is excreted in stool vs. urine
90% stool
10% urine
how does the liver carry out detoxification
takes fat soluble toxins and undergoes several steps to make them water soluble waste products which can be eliminated by the body in stool or urine
what does a bilirubin LFT assess
transport from hepatocytes to biliary system
what do aminotransferases LFTs assess
hepatocyte damage
GGTs alone assess
drugs (e.g. antiepileptics)
cholestasis can be assessed by what LFTs
GGT and alkaline phosphatase
what LFTs test the protein synthesis/synthetic function of the liver
albumin
prothrombin time
potential causes of jaundice
blockages of bile ducts due to
- gallstones
- tumours of head of the pancreas
- ampullary lesions
