Liver Physiology Flashcards
State normal liver functions
- Amino acid, carbohydrate and lipid metabolism
- Storage of proteins, glycogen, vitamins and metals
- Plasm Protein and enzyme synthesis
- Detoxification
- Iron Storage
- B12 storage
- Endocrine function (IGF1,2)
- Immune functions
The primary functional unit of the liver is a ???. There are normally how many of these?
- Lobules
- 50,000-100,000
At the central of the hexagonal shaped lobules you have a ???????. In between the lobules you will find the ??????, which consists of ????, ???? and ?????.
- Central vein - which is a branch of the hepatic vein
- Braches of hepatic artery
- Branches of bile duct
- Branch of portal vein
There are two major blood supplies for the liver, what vessels are they and what is different about them?
- Hepatic artery proper - delivers 30% of blood and is oxygenated blood
- Hepatic portal vein - delivers 70% of blood and is deoxygenated and nutrient rich
The major cells in the liver are called ??????. They are separated by ???????
hepatocytes
Sinusoids.
Hepatocytes through selective absorption are able to regulate levels of certain ???????????. They also secrete ????
Nutrients
BILE
The sinusoid are specialised capillarie - they are also lined by endothelial cells. What two features do they have that differentiates them?
They are fenestrated.
They also lack a basement membrane.
Blood from the portal vein and hepatic artery branches both travel down the sinusoids - causing blood to mix. Blood then leaves the sinsoids and enters the central vein, which drains into?
The hepatic portal vein
Bile is scereted by hepatocytes, which then drains into ?????. Bile then drains from the canaliculi into one of the ?????? s at the corners of liver lobules. Then they travel to one of the ???????, which unite to form the ?????????. From here it can flow into either the ??????? or the ????????.
- Bile duct
- Left or Right hepatic duct
- Common bile duct
- Cystic duct of the gallbladder
- Bile duct
Summarise the cells you would expect to find in the liver parenchyma
- Hepatocytes
- Endothelial cells
- Kupffer cells
- Perisinusodial cells (fat storingcells)
- Liver-associated lymphocytes
How much blood flows through from the portal vein into the sinusoids per minute?
1050ml
It is normal to find some spaces between sinusoids and surronding hepatic cells. What are these spaces called, and what is their function?
Spaces of Disse/Perisinusodial spaces
- Connected by many lymphatic vessels which remove excess fluid from these spaces
What is the primary fibre found in liver connective tissue? What collagen is it made from?
- Reticular fibres - formed by type 3 collagen
Cirrhoris is definied by 3 factors:
- Diffuse process - effects the entire liver
- FIbrosis - formation of excess connective tissue
- Nodule formation - basically causes the normal parenchyma to be segmented into subdivisions
State causes of cirrhoris
Alcohol or Alcohol-like (i.e. non-alcoholic fatty liver disease) = 60-70%
Hepatitis = 10%
Biliary disease = 5%
Unknown = 10-15%
Haemochromatosis = 5% (iron build up)
Cirrhoris itself isn’t really a disease, but an end-stage pathology as a result of a long-standing liver condition; such as ?????
Hepatitis
Chronic Alcohism.
Summarise the pathogenesis of cirrhoris
Define Cirrhoris
- Late stage complication of various liver diseases, characterised by hepatic fibrosis and deformation of the normal liver parenchyma, as well as by the formation of nodules that give the liver a segmented appearance
- the nodules are clumps of hepatocytes which have grouped together and have become walled off from other hepatocytes by fibrous connective tissue
Explain the mechanisms by which cirrhosis occurs
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State complications of cirrhosis
- Portal hypertension
- Liver failure
As fibrotic tissue in the space of disses start to build up, it compresses the sinusoids, increasing pressure in the sinusoids. This increases the tendency for fluid to be pushed into the peritoneal cavity. What is this known as?
Ascites
Another result of portal hypertension is Hepatic encephalopathy. What is this?
- Due to impaired liver function, certain toxins not broken down properly
- These build up in bloodstream, and if they enter the brain can cause personality changes, intellectual impairment and a depressed level of connsciousness.
As portal hypertension occurs, there is an extensive network of new portosystemic collaterals that divert a large fraction or portal blood to the systemic circulation, bypassing the liver. Furthemore, there is peripheral and splanchnic ?????
Vasodilatation.
Another result of cirrhosis is what?
Splenomegaly
Increased pressure in the portal venous system results in development of swollen veins called?
Varices
What are varices?
varices are extremely dilated sub-mucosal veins; commonly due to cirrhosis.
Why is there peripheral and splanchnic artery vasodilaton, and why does this aggrevate portal hypertension?
- Liver blood flow is inefficient, so other arteries dilate to increase blood flow,
- however, this doesnt change the fact that the portal vein branches are still heavily constricted, so the problem is made even worse by trying to squeeze more blood through
Where do varices from cihrossis most often form? Why does this occur
- at the oesophagus
- When portal hypertension causes a back of blood, other pathways will be sought through smaller veins such as the lower part of the oesophagys
- These thin walls ballon with the aded blood - and have the risk of rupture
How is portal hypertesnion diagnosed?
- Often diagnosed on the presentation of ascites or varices as seen during a physical exam of the abdomen, or when there is suggestion of hepatic encephalopathy
- Endoscopy is mots useful investigation to determine if varrices are present - once the diagnosis of cirrhosis is made, endoscopy should be performed to look for oesophageal varices
- Ultrasound can show features like spenomegaly or collateral vessels
- CT and MRI angiography
- Portal cenous pressures - balloon cathether inserted via transjugular route to measure pressure
Treatment for portal hypertension
- focused on the prevention of variceal haemorrhage
For prophylaxis of beta blockers:
- Propanolol is effective in reduce venous portal pressures and that in the varrices
During bleeding:
- endoscoping banding
- vasoactive drugs (such as Telipressin) - causes vasconstriction of the varices and prevent further bleeding.
The hepatic lobule can be described in terms of metabolic “zones” called sinuses. The presmise that brances of the portal triad will supply the lobules; the zone of the lobule nearest to th eentering blood supply will receive the most ????????, whilst the zone of the lobule furthest away from the arterioles will have the poorest supply of ????????. Furthermore, the cells at the centre of the acinus “zone 1” are the first to “see) and potentially absorb blood borne ???? and???? into the portal blood from the small intestine.
- oxygen - which is where most of the metabolic action of the liver takes place
- oxygen - meaning the zone 3 is more susceptible to isachemic damage
- toxins and pathogens
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