Liver Physiology

Question 1

State normal liver functions

Answer 1

• 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

Question 2

The primary functional unit of the liver is a ???. There are normally how many of these?

Answer 2

• Lobules
• 50,000-100,000

Question 3

At the central of the hexagonal shaped lobules you have a ???????. In between the lobules you will find the ??????, which consists of ????, ???? and ?????.

Answer 3

• Central vein - which is a branch of the hepatic vein
• Braches of hepatic artery
• Branches of bile duct
• Branch of portal vein

Question 4

There are two major blood supplies for the liver, what vessels are they and what is different about them?

Answer 4

• Hepatic artery proper - delivers 30% of blood and is oxygenated blood
• Hepatic portal vein - delivers 70% of blood and is deoxygenated and nutrient rich

Question 5

The major cells in the liver are called ??????. They are separated by ???????

Answer 5

hepatocytes

Sinusoids.

Question 6

Hepatocytes through selective absorption are able to regulate levels of certain ???????????. They also secrete ????

Answer 6

Nutrients

BILE

Question 7

The sinusoid are specialised capillarie - they are also lined by endothelial cells. What two features do they have that differentiates them?

Answer 7

They are fenestrated.

They also lack a basement membrane.

Question 8

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?

Answer 8

The hepatic portal vein

Question 9

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 ????????.

Answer 9

• Bile duct
• Left or Right hepatic duct
• Common bile duct
• Cystic duct of the gallbladder
• Bile duct

Question 10

Summarise the cells you would expect to find in the liver parenchyma

Answer 10

• Hepatocytes
• Endothelial cells
• Kupffer cells
• Perisinusodial cells (fat storingcells)
• Liver-associated lymphocytes

Question 11

How much blood flows through from the portal vein into the sinusoids per minute?

Answer 11

1050ml

Question 12

It is normal to find some spaces between sinusoids and surronding hepatic cells. What are these spaces called, and what is their function?

Answer 12

Spaces of Disse/Perisinusodial spaces

• Connected by many lymphatic vessels which remove excess fluid from these spaces

Question 13

What is the primary fibre found in liver connective tissue? What collagen is it made from?

Answer 13

• Reticular fibres - formed by type 3 collagen

Question 14

Cirrhoris is definied by 3 factors:

Answer 14

• Diffuse process - effects the entire liver
• FIbrosis - formation of excess connective tissue
• Nodule formation - basically causes the normal parenchyma to be segmented into subdivisions

Question 15

State causes of cirrhoris

Answer 15

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)

Question 16

Cirrhoris itself isn’t really a disease, but an end-stage pathology as a result of a long-standing liver condition; such as ?????

Answer 16

Hepatitis

Chronic Alcohism.

Question 17

Summarise the pathogenesis of cirrhoris

Question 18

Define Cirrhoris

Answer 18

• 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

Question 19

Explain the mechanisms by which cirrhosis occurs

Answer 19

SEE MIND MAP FOR MORE DETAIL

Question 20

State complications of cirrhosis

Answer 20

• Portal hypertension
• Liver failure

Question 21

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?

Answer 21

Ascites

Question 22

Another result of portal hypertension is Hepatic encephalopathy. What is this?

Answer 22

• 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.

Question 23

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 ?????

Answer 23

Vasodilatation.

Question 24

Another result of cirrhosis is what?

Answer 24

Splenomegaly

Question 25

Increased pressure in the portal venous system results in development of swollen veins called?

Answer 25

Varices

Question 26

What are varices?

Answer 26

varices are extremely dilated sub-mucosal veins; commonly due to cirrhosis.

Question 27

Why is there peripheral and splanchnic artery vasodilaton, and why does this aggrevate portal hypertension?

Answer 27

• 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

Question 28

Where do varices from cihrossis most often form? Why does this occur

Answer 28

• 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

Question 29

How is portal hypertesnion diagnosed?

Answer 29

• 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

Question 30

Treatment for portal hypertension

Answer 30

• 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.

Question 31

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.

Answer 31

• 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

Question 32

Label

Answer 32