Hepatobiliary System, Pt. 2 Flashcards
What are the major functions of the liver?
- bile synthesis and secretion
- bilirubin metabolism
- carbohydrate metabolism
- lipid metabolism
- protein synthesis
- ammonia metabolism
- xenobiotic metabolism
How is bilirubin normally metabolized and eliminated?
- RBC enters spleen and is phagocytized
- hemoglobulin is broken down into heme and globulin
- globulin is further broken down into amino acids
- heme is broken down into iron and porphyrin, which becomes unconjugated bilirubin
- unconjugated bilirubin binds to albumin and is transported to hepatocytes, which conjugate it and allows to be excreted in the biliary system
What is a common sequel to bilirubin metabolism dysfunction? How does it look grossly?
hyperbilirubinemia = icterus (jaundice)
yellow staining of skin, mucous membranes, and fat
What are 3 types of causes for icterus?
- prehepatic
- hepatic
- posthepatic
What are 2 causes of prehepatic icterus?
- increased unconjugated bilirubin
- hemolysis (immune-mediated, infectious, metabolic, trauma, toxin)
What are 2 causes of hepatic icterus?
- defective uptake or conjugation of conjugated or unconjugated bilirubin
- liver disease or congenital anomalies
What are 2 causes of posthepatic icterus?
- increased conjugated bilirubin
- bile duct obstruction (thrombus, stone, neoplasia)
What causes canalicular plugging? How does it look histologically?
dysfunction of bilirubin metabolism causes it to accumulate in hepatic canaliculi
brown, amorphous globular pigments (bilirubin) in canaliculi
How does the liver control carbohydrate metabolism?
regulates plasma glucose concentration by mediating glycogenolysis and glycogenesis
What are 2 causes of glycogen accumulation in the liver?
- excess glucocorticoids (steroid hepatopathy) in dogs - endogenous (Cushings = increased cortisol) and exogenous
- glycogen storage diseases
How does glycogen accumulation in the liver affect its color?
diffuse yellow-tan color changes
- glucocorticoid-induced hepatopathy, dog
How does glycogen accumulation in the liver appear histologically?
amorphous pink strands within swollen hepatocytes with central nuclei
- glucocorticoid-induced hepatopathy, dog
How does lipid metabolism occur in the healthy liver? How does insulin affect this process?
- dietary sugary causes de novo lipogenesis, forming fatty acids within the liver
- triglycerides from adipose tissue becomes FFA that are delivered to the liver and metabolized into fatty acids
- lipids within the liver decrease β-oxidation in mitochondria and are transported to tissue by VLDL particles
insulin will block the transformation of triglycerides into FFA to decrease fatty acid metabolism in the liver and blood glucose levels
What happens to lipid metabolism within the diseased liver?
increased dietary sugar, obesity, and insulin resistance will increase the rapid formation of FFA and triglyceride accumulation in the liver
- the liver will be unable to keep up with transportation to tissues, which leads to triglyceride accumulation and lipidosis
What are 6 causes of hepatic lipidosis (fatty change/steatosis)
- high-fat or cholesterol diet
- negative energy balance (secondary to anorexia, pregnancy) causes the liver to work harder to move lipids
- toxin
- ketosis (DM)
- endocrine disordered (DM, hypothyroidism)
- idiopathic