Special pathology - hepatic disease Flashcards
The liver of domestic animals has how many lobes?
Each liver lobe is composed of ?
5-6, species dependently
Each liver lobe is composed of lobules. There are approx. 700,000 lobules in a liver.
the portal triad consists of?
hepatic artery
portal vein
bile duct
Hepatic Sinusoid
Vascular spaces, termed sinusoids, run between the hepatic plates (cords).
main exocrine function of the liver
Production and excretion of bile
Bile is composed of: (5)
-water
-cholesterol
-bile acids
-bilirubin
-inorganic ions, other constituents
purposes for bile synthesis: (3)
excretory route (for metabolic by-products)
facilitation of digestion
buffers to neutralize acids
Functions of bile acids: (3)
-maintenance of cholesterol homeostasis
-stimulation of bile flow
-intestinal absorption of fats and fat-soluble vitamins
Bile acids are synthesized in the liver from cholesterol and are conjugated with
glycine or taurine before being excreted into the bile, in order to facilitate their interaction with other components of the bile and
to prevent precipitation into calculi when they are secreted.
The quantities of bile acids required far exceed
the liver’s capacity to produce them!
Thus, using the enterohepatic circulation, bile acids are reabsorbed from the ileum,
extracted from the portal blood, and resecreted into bile.
Interruption of this process results in fat malabsorption and a deficiency of fat-soluble vitamins.
Bilirubin is produced from
the metabolic degradation of hemoglobin.
The majority of bilirubin is derived from normal extrahepatic breakdown of senescent erythrocytes with a minor contribution from degradation of tissue heme-containing proteins.
Gut bacteria deconjugate bilirubin in the GI tract and degrade it to
colorless urobilinogens.
The urobilinogens are excreted in the feces, with minimal reabsorption and excretion into urine too.
Residual urobilinogen is metabolized by bacteria into the brown pigment called
stercobilin, imparting the typical color to feces.
Name 4 plasma lipids.
cholesterol,
triglycerides,
phospholipids, and
lipoproteins
Hepatocytes can synthesize fatty acids when energy levels are high, and they can oxidize fatty acids as an energy source when necessary.
xenobiotic definition
all substances foreign to the body
e.g. drugs, toxins etc.
Cytochrome P450 enzymes of the smooth endoplasmic reticulum (microsomes) of the hepatocytes serve as the major site of metabolism of these substances in preparation for excretion in bile or urine.
what is Cytochrome P450
a major group of hepatic enzymes that play a significant role in the detoxification of xenobiotics among other tasks
Cytochrome P450 enzymes of the smooth endoplasmic reticulum (microsomes) of the hepatocytes serve as the major site of metabolism of xenobiotics in preparation
for excretion in bile or urine
endogenous substances (steroids that are lipophilic)
require conversion to ? for elimination from the body
require conversion to water-soluble forms for elimination from the body
The liver is responsible for synthesis of approximately ?% of body proteins.
The liver is responsible for synthesis of approximately 15% of body proteins.
Synthesis of the majority of plasma proteins occurs mainly within
the rough endoplasmic reticulum of hepatocytes.
Proteins produced in the liver include plasma proteins:
(7)
albumin
variety of transport proteins
lipoproteins
clotting factors II, V, and VII to XIII
plasminogen
some acute phase proteins (e.g. CRP, SAA)
components of the complement system (C1- C9)
Highly toxic ammonia is generated through catabolism of
amino acids.
Metabolic conversion of ammonia into urea, a far less toxic compound, occurs through the urea cycle, which occurs almost exclusively in the liver.
Urea then enters the systemic circulation (blood urea nitrogen) and is excreted in the urine.
The liver has a significant immune function involved in:
(3)
systemic
local
mucosal immunity
Hepatocytes participate in the response to systemic inflammation through the synthess and release of
acute phase proteins.
Approximately ?% of the cells in the liver belong to the adaptive immune system or the innate immune system.
Approximately 10% of the cells in the liver belong to the adaptive immune system (T and B lymphocytes) or the innate immune system (Kupffer cells, natural killer lymphocytes, and natural killer T lymphocytes).
Compared with other organs, the liver is particularly enriched with cells of the
innate immune system, likely a result of the fact it is the site where foreign antigens from the gastrointestinal tract first encounter the innate immune system defenses.
The liver contains the largest pool of (2)
mononuclear phagocytes and natural killer cells in the body in most species.
The Kupffer cells provide the first line of defense against infectious agents, endotoxins, and foreign material absorbed from the intestines before they gain access to the systemic circulation.
Disposal of waste molecules such as (2)? and deletion of activated effector T lymphocytes are also important functions of the liver.
e.g., products of inflammation such as cytokines and immunoglobulins and deletion of activated effector T lymphocytes are also important functions.
The liver is also involved in transport of secretory
immunoglobulin A (IgA), the primary IgG on mucosal surfaces, from plasma cells into the biliary tree an dintestine.
Mechanisms of Liver Injury (6)
- Metabolic bioactivation of chemicals via cytochrome P450 to reactive species
*Stimulation of autoimmunity - Stimulation of apoptosis
*Disruption of calcium homeostasis leading to cell surface blebbing and lysis
*Canalicular injury
*Mitochondrial injury
What is surface blebbing?
A bleb is an irregular bulge in the plasma membrane of a cell caused by localized decoupling of the cytoskeleton from the plasma membrane. The bulge eventually blebs off from the parent plasma membrane taking part of the cytoplasm with it.
Acute Hepatitis is
Inflammation of the liver parenchyma
Acute Hepatitis is characterized by: (3)
-inflammation
-hepatocellular necrosis
-apoptosis
In many forms of acute hepatitis- what cell types accumulate?
neutrophils accumulate in response to the usual chemotactic stimuli
Random foci of neutrophilic hepatitis, as a consequence of embolic localization of bacteria, are relatively common in all species.
In neonates—especially calves, lambs, and foals—bacteria, such as Escherichia coli, usually seed the liver via
the umbilical veins or less often the portal venous or
hepatic arterial systems.
Acute hepatitis produced by viral infections such as?
herpesvirus
- more frequently characterized by a random distribution of necrosis and apoptosis with minimal inflammation or infiltration of lymphocytes.
Chronic Hepatitis is
continued hepatic inflammation as a result of persistence of an antigenic stimulus.
Chronic Hepatitis is characterized by: (3)
fibrosis;
accumulation of mononuclear inflammatory cells,
including lymphocytes, macrophages, and plasma cells;
frequently- regeneration
Granulomatous hepatitis is
refers to the presence of granulomas in the liver.
Liver granulomas are common and are the result of an inflammatory reaction to numerous noxious stimuli.
Chronic suppurative hepatitis is usually manifested as
discrete or multiple abscesses.
Focal lesions, such as abscesses or granulomas, often are sufficiently localized so that they do not alter liver function.
Diffuse and severe chronic hepatitis usually leads to loss of
hepatic parenchyma, and architectural distortion of the liver as a consequence of fibrosis and nodular parenchymal regeneration.
Nonspecific Reactive Hepatitis is (3)
a diffuse process
distributed throughout the liver
response to some systemic illness most often within the gastrointestinal tract, or is the residuum of prior liver
inflammation
Nonspecific Reactive Hepatitis Represents a
non-specific response to a variety of extrahepatic disease processes,
previous or ongoing febrile illnesses and/or inflammation somewhere in the splanchnic area.
The inflammatory infiltrate is mostly localized in the portal area during this non-specific reaction of the liver.
Cholangitis is
Inflammation of the biliary ducts (either intrahepatic or extrahepatic).
There are Several patterns of cholangitis.
The inflammatory cell population and the degree of fibrosis will vary with the type and duration of injury.
Neutrophilic Cholangitis is the
most common type of cholangitis.
There are acute and chronic forms.
Neutrophilic Cholangitis is
characterized by the presence of neutrophils within the lumen or epithelium of the bile ducts.
Neutrophilic Cholangitis is caused by
caused by ascending bacterial infections from the intestine.
Bacterial culture from gallbladder bile is the most rewarding approach and most often reveals
infection with enteric organisms such as Escherichia coli, Enterococcus, Bacteroides, Streptococcus, or Clostridium.
Lymphocytic cholangitis occurs most often in
cats.
Destructive Cholangitis is
an uncommon syndrome characterized by necrosis of the epithelium of bile ducts.
Inflammation is often present around the areas of biliary destruction and may extend along cholangioles outside of the portal tract.
Certain chemicals, such as trimethoprim-sulfa, have been implicated in this syndrome in dogs.
Cholangiohepatitis is when
Inflammation affects both the biliary ducts and hepatic parenchyma.
the principal cellular targets of most liver diseases are (3)
The epithelial cells of the liver, hepatocytes and biliary epithelium.
Sublethal injury to hepatocytes is characterized by (3)
cell swelling (hydropic degeneration),
steatosis,
or atrophy
lipofuscin is
the name given to fine yellow-brown pigment granules composed of lipid-containing residues of lysosomal digestion.
this pigment can often be found in affected cells and associated phagocytes after sublethal liver injury.
Random Hepatocellular Degeneration and/or Necrosis can be typical of
many infectious agents, including viruses, bacteria, and certain protozoa.
Centrilobular Degeneration and/or Necrosis is
particularly common.
this portion of the lobule receives the least oxygenated blood and is therefore susceptible to hypoxia.