The Liver - (1) Flashcards
what is the gross anatomy of the liver?
- 2 main lobes to the liver
- 8 independent units
- Coronary ligament attaches the liver to the anterior aspect of the abdomen.
what happens if there is problem in one of the 8 units?
means that area can be worked on without the other segments being impacted
what are the features of the blood supply to the liver?
- rich blood supply
25% of resting cardiac output - dual blood supply
20% arterial blood from the hepatic artery - 80% venous blood draining from the gut through the hepatic portal vein
what is the purpose of having two blood supplies of the liver?
- oxygenated blood is coming from the hepatic artery
- the liver has a huge metabolic role and the hepatic portal vein brings all the blood with substances absorbed from the gut to the liver
how well oxygenated is the blood supply to the liver?
poorly compared to the rest of the body due to the hepatic portal vein
what are the microanatomy structures of the liver split into?
- morphological
- functional
what is a feature of the lobules?
- portal triads
- consists of hepatic portal vein, hepatic artery, bile duct.
- Blood flows towards the central canal (and bile the opposite way).
where are periportal hepatocytes present?
where are centrilobular hepatocytes present?
- Periportal hepatocytes are featured near the portal triad
- Centrilobular hepatocytes are featured near the central canal
what are the processes the liver has a main function in?
- digestion
- biosynthesis
- energy metabolism
- degradation
main cell types in liver
- Hepatocytes
- Endothelial cells
- Cholangiocytes
- Kupffer cells
- Hepatic stellate cells
what are the structural features of the hepatocytes?
Hepatocytes are large cells with pale and rounded nuclei.
what are the structural features of the Kupffer cells or Hepatic stellate cells?
Flattened, dense cell nuclei that appear to be in the sinusoids
what is an acinis?
Defined as a unit of hepatocytes divided into zones dependant on proximity to arterial blood supply.
what do the different zones of the acinis near to?
what are the different zones predisposed to?
Zone 1 – close to portal triad – predisposed to viral hepatitis.
Zone 2 – close to central canal – predisposed to ischaemia.
what cells produce bile?
and where does the bile flow?
- Bile is produced by hepatocytes
- flows along canaliculus to the bile duct.
what are the non parenchymal cells?
- hepatic stellate cells
- sinusoidal endothelial cells
- kupffer cells
function of hepatic stellate cells ?
- Vitamin A storage
- Activation = ECM production
function of sinusoidal endothelial cells ?
- Fenestrated – allows lipid and other large molecule movement to and from hepatocytes
function of kupffer cells ?
- Phagocytosis (inc. RBC breakdown)
- Secretion of cytokines that promote Hepatic sellate Cells Activation - proliferation, contraction and fibrogenesis
what are pathological implications of non parenchymal cells?
liver cirrosis
what is the livers role in the metabolism of carbs?
- Important to control blood glucose
- Stored as glycogen mainly in muscle and liver
- Breakdown liver glycogen maintains blood glucose concentration between meals
what happens to the lactate produced by the muscle cells?*****
- lactate is converted to pyruvate
by lactate dehydrogenase - the pyruvate is then converted to glucose by gluconeogenesis
- the glucose then returns back to the muscle cell to be used again in glycolysis
How might ‘hitting the wall’ when running a marathon be
associated with liver function?
if you run out of glycogen in the liver
how does the liver metabolise amino acids?
- the amino acid enters the liver from the diet eg. alanine
- using keto acids transamination reactions happen which results in pyruvate
- catalysed by transaminases
- different keto acids result in new amino acids
what happens in deamination?
the muscle utilise amino acids to produce glucose for energy
what are the problems of deamination and what is the solution?
- To convert pyruvate to glucose requires energy
- To remove nitrogen as urea requires energy
the solution is to transfer the amino acid to the liver
what happens in the glucose alanine cycle (deamination) : ****
- glutamate from amino acid breakdown goes to alanine in the muscle cell
- in the liver this undergoes a transaminase reaction in the liver to make pyruvate and glutamate
- the pyruvate is converted to glucose
- the glutamate is converted to urea
Glutamate metabolism actually produces NH3 which is very toxic to the body (especially brain), so liver converts it to water soluble urea.
how does the liver metabolise fats?
- starts with a triglyceride which is broken down into a fatty acid
- the fatty acids undergo beta oxidation
- then two molecules of acetyl Co- A are condensed enzymically to make HMG -CoA
- HMG - CoA is then cleaved to make free acetoacetate and acetyl CoA
how does the liver make lipo proteins de novo
- glucose entering the liver can be converted to several components of lipoproteins
- glycerol, fatty acids and cholesterol
- Glucose can be directly converted to glycerol
- or glucose can be converted to acetyl CoA via the TCA cycle via pyruvate
- Acetyl CoA can be converted to cholesterol using HMG CoA
- converted to fatty acids (via the intermediate malonyl CoA
how does the liver make lipo proteins from glycerol?
- glycerol gets converted to tri acyl glycerol
- which added to apoproteins, phospholipids and cholestrol makes lipoproteins
how does the liver make HDL and LDL?
- the liver can produce HDL
this is good cholesterol the major role is to mop up excess cholesterol in the circulation and return to the liver
(high protein but low fat content) - the liver can also produce VLDL which delivers fatty acids to body tissues
- then it is converted to LDL which is very high in cholesterol
- the LDL then delivers this cholesterol to tissues
- tissues use the cholesterol to make hormones and to maintain cell membrane integrity
- excess cholesterol goes back to the liver
what vitamins does the liver store?
- Storage of fat soluble vitamins (A,D,E,K). Stores sufficient 6-12 month except Vit K where store is small
- Storage of iron as ferritin.
what is vit K needed for?
Vit K essential blood clotting
