Special Path - Liver Basics Flashcards
What are two sources of blood for the liver?
(1) 2/3rd from Portal Vein - drains GI tract
(2) 1/3rd Hepatic artery
* dual blood supply
Blood leaves the liver from what two vessels?
Hepatic Vein and Vena Cava
Functional subunit of the liver is? Provide description
Lobule - hexagonal and 1-2mmwide; central vein is at the center and portal areas are at the periphery
Portal areas contain?
Bile ducts, portal vein, hepatic artery, nerves, and lymph vessels
How are hepatocytes arranged?
Arranged in branching plates which radiate from the central vein and are separated by sinusoids (blood spaces)
Sinusoids are bounded by endothelial cells which are separated from hepatocyte microvilli by….?
Space of disse
What can pass through the space of disse?
RBCs are retained in the sinusoids but large molecules can pass through into hepatocytes
Damage (like fibrosis) in the space of disse does what?
Reduces resorption by hepatocytes and has serious consequences for liver function
Sinusoids contain resident macrophages which have a variety of functions including phagocytosis and release of cytokines. Another name for these resident macropahges is?
Kupffer cells
What is the purpose of hepatic stellate cells and where are they located?
Hepatic stellate cells are located in the space of disse and differentiate into myofibroblasts following injury and are the main source of hepatic fibrosis.
The main source of hepatic fibrosis is from what type of cell?
Hepatic stellate cells
Describe the flow of bile
It flows in the opposite direction to blood.
Bile canaliculi –> centrilobular areas –> bile ducts in portal areas –> gall bladder –> common bile duct
Function of hepatocytes (4):
(1) Synthesis of cholesterol, bile acids, glycogen
(2) metabolism and preparation of substances for excretion via bile (ex. pigments or steroid hormones)
(3) metabolism of fatty acids
(4) synthesis of proteins (albumin, clotting factors, firbinogen, lipoproteins)
Function of bile canaliculus
Transport bile
Function of sinusoids
Kupffer cells phagocytosis of foreign material from blood
Abnormalities of the liver are not usually detected until what?
Majority of hepatic functional mass is lost
All clotting factors except factor ____ are synthesized in the liver.
VIII
List clotting abnormalities of the liver (3):
(1) Decreased synthesis of clotting factors
(2) Decreased clearance of fibrin degradation products, activated coagulation factors and plasminogen
(3) Metabolic changes secondary to liver disease can affect platelet function
Liver dysfunction - What is hypoalbuminemia?
Severe chronic disease (decreased synthesis and increased loss secondary to portal hypertension)
Liver dysfunction - Photosensitization
Hepatic disease or biliary obstruction decreases normal excretion of phylloerythrin (a photodynamic product of chlorophyll produced in herbivores) in bile –> Increased phylloerythrin in serum and concentration in cutaneous tissues –> UV light activates phylloerythrin and results in cutaneous lesions usually in hairless areas
Liver dysfunction - Hepatic Encephalopathy (CNS disturbance caused by abnormal neurotransmission)
Increased concentrations of ammonia derived from amines absorbed in GIT may be responsible.
Occurs when insufficient liver function remains for metabolism (end stage liver in horses and ruminants) or significant portion of blood bypasses the liver (congential portosystemic shunts in dogs and cats).
It can result from shunting of blood within regenerative nodules in end stage liver disease in dogs and cats.
Congenital portosystemic shutns in dogs and cats can lead to?
Hepatic Encephalopathy
Liver dysfunction - Hyperbilirubinemia (icterus) may occur as a result of?
May occur as a result of severe hepatic disease, cholestasis, intravascular or extravascular hemolysis.
Intrahepatic cholestasis is what and occurs as a result of what?
Intrahepatic cholestasis is decreased secretion of bile across hepatocyte membrane. It occurs as a result of disorders of hepatocytes (toxins, bacteria, viruses, ischemia)
Extrahepatic cholestasis is a result of what?
Result of obstruction of bile flow (neoplasia, parasites, inflammation, calculi)
Three responses to liver injury are:
(1) Fibrosis
(2) hepatocellular regeneration
(3) Bile duct proliferation
What is cholestasis?
When bile cannot flow from the liver to the duodenum
The combination of what two things is responsible for the nodularity (coarse or fine) of chronic hepatic disease?
Combination of regeneration and fibrosis
Is advanced fibrosis reversible?
No, it is irreversible, and can be lethal
Hepatic fibrosis is an increase of ____ within lesions and space of Disse.
(1) Fibrillar collagen (type I and III)
(2) Non-fibrillar collagen (type 18)
(3) Extracellular matix (proteoglycans, fibronectin, hyaluronic acid)
Severely fibrotic liver can contain ___x as much collagen and other extracellularm atrix as normal.
6x
Hepatic stellate cells are activated by cytokines to do what following hepatic injury?
Change from lipid storage cells to myofibroblatsic cells which synthesize collagen following hepatic injury.
Can the site of fibrosis within the hepatic lobule be indicative of the type of insult?
Yes, however chronic or severe injury often produces fibrosis affecting most areas of the liver
Centrilobular fibrosis can result from ____
chronic right sided heart failure or toxic injury
Periportal fibrosis can result from ____
chronic inflammation, toxins (some can affect periportal hepatocytes), chornic biliary obstruction
Bridging fibrosis is?
Fibrosis that extends from one portal area to another or from portal areas to centrilobular areas. Associated with impaired hepatic function
Multifocal hepatic fibrosis
Foci of fibrosis randomly scattered throughout the parenchyma
Diffuse hepatic fibrosis
Affects all regions of the lobule and is present throughout the liver
End stage liver disease (cirrhosis) is marked by?
Diffuse fibrosis with formation of regenerative nodules and often bile duct hyperplasia
Can you determine the cause or initial pattern of fibrosis in end stage liver disease?
No
Post necrotic scarring
A single event of widespread necrosis (usually centrilobularo r massive) may be followed by fibrosis and condensation of connective tissue stroma resulting in formation of bands of thick connective tissue.
As much as ___ of the liver can be regenerated in a healthy animal.
2/3rds
In order for regeneration to take place in an orderly fashion, the affected area must have an intact _____.
reticulin framework
In chronic liver disease, hepatocellular regeneration is typically ____.
Nodular
Regenerative nodules restore ___ but not ____. Therefore, normal blood flow cannot be _____.
Regenerative nodules restore mass but not function. Therefore, normal blood flow and bile flow cannot be reestablished.
Regeneration may be the result of proliferation of _____ or ______.
Regeneration may be the result of proliferation of mature hepatocytes (enlargement of existing lobules) or hepatocyte stem cells (oval cells).