Chemical Pathology: Liver Anatomy and Architecture

Questions and Answers

What is the primary function of the hepatic artery in liver blood supply?

The hepatic artery supplies oxygenated blood to the liver.

Describe the structural organization of a hepatic lobule.

A hepatic lobule is a hexagonal unit surrounded by connective tissue septae, with portal tracts and a central hepatic venule.

What are the three functional zones of the hepatic acinus based on oxygen content?

The three functional zones are Zone I (Periportal), Zone II (Mediolobular), and Zone III (Centrilobular).

What happens to unconjugated bilirubin in the liver?

Unconjugated bilirubin is conjugated with glucuronic acid by UDPGT enzymes to form conjugated bilirubin. Signup and view all the answers

How are primary bile acids produced and utilized in the liver?

The liver produces primary bile acids from cholesterol and conjugates them to increase solubility for bile transport. Signup and view all the answers

What is enterohepatic circulation, and why is it important for bile acids?

Enterohepatic circulation is the process where bile acids are reabsorbed from the GIT, returned to the liver, and reused. Signup and view all the answers

What are the main risk factors for developing NAFLD?

The main risk factors for developing NAFLD include central obesity, type 2 diabetes mellitus, dyslipidemia, and metabolic syndrome. Signup and view all the answers

Describe the histological features of cirrhosis.

Histologically, cirrhosis is characterized by fibrosis and regenerating nodules, with alcoholic, cholestatic, and congestive cirrhosis being micronodular, while post-viral hepatitis cirrhosis is macronodular. Signup and view all the answers

What role do bacteria play in the conversion of bile acids in the GIT?

Bacteria in the GIT convert primary bile acids into secondary bile acids. Signup and view all the answers

What is the common pathway leading to portal hypertension in cirrhosis?

The derangement of microvasculature due to cirrhosis leads to portal hypertension and causes shunting of portal blood to systemic circulation. Signup and view all the answers

Define the composition and function of bile acids.

Bile acids are amphipathic molecules formed from cholesterol, helping to solubilize dietary fats and cholesterol for excretion. Signup and view all the answers

What is the significance of urobilinogen in bilirubin metabolism?

Urobilinogen is a product of conjugated bilirubin conversion in the colon, and it can be reabsorbed into the portal circulation. Signup and view all the answers

List two common causes of cirrhosis.

Chronic viral hepatitis (hepatitis B, C) and alcoholic liver disease are two common causes of cirrhosis. Signup and view all the answers

What are some clinical symptoms of compensated cirrhosis?

Clinical symptoms of compensated cirrhosis include non-specific weakness, fatigue, loss of appetite, and nausea. Signup and view all the answers

In terms of liver blood flow, differentiate between the hepatic vein and portal vein.

The hepatic vein carries venous drainage away from the liver, while the portal vein brings non-oxygenated blood from the digestive organs. Signup and view all the answers

Identify a symptom of decompensated cirrhosis related to the urinary system.

A symptom of decompensated cirrhosis related to the urinary system is dark urine. Signup and view all the answers

What lifestyle changes are recommended for treating NAFLD?

Recommended lifestyle changes for treating NAFLD include a low-calorie and low-fat diet, regular exercise, and gradual weight loss. Signup and view all the answers

How does hepatic encephalopathy manifest in early stages?

In the early stages, hepatic encephalopathy may manifest as irritability and personality or behavioral changes. Signup and view all the answers

What is the main laboratory test result that indicates hemolysis in patients with sickle cell anemia?

Increased reticulocyte count indicates hemolysis in patients with sickle cell anemia. Signup and view all the answers

Identify one cause of ineffective erythropoiesis and explain how it affects red blood cell production.

Megaloblastic anemia is a cause of ineffective erythropoiesis that leads to impaired red blood cell production due to defective DNA synthesis. Signup and view all the answers

What is the significance of increased unconjugated bilirubin in hemolytic anemia?

Increased unconjugated bilirubin indicates that the rate of bilirubin production exceeds the liver's capacity to conjugate it. Signup and view all the answers

How would urine bilirubin levels differ in pre-hepatic and post-hepatic jaundice?

Urine bilirubin is negative in pre-hepatic jaundice and positive in post-hepatic jaundice. Signup and view all the answers

What laboratory findings would suggest post-hepatic jaundice?

Post-hepatic jaundice is suggested by increased conjugated bilirubin in serum and urine, and decreased urobilinogen in stools. Signup and view all the answers

What are the implications of bile duct carcinoma for jaundice and liver enzyme levels?

Bile duct carcinoma can cause jaundice due to obstruction and typically results in increased alkaline phosphatase (ALP) and GGT levels. Signup and view all the answers

Explain how Gilbert’s syndrome affects bilirubin levels in affected individuals.

Gilbert's syndrome causes mildly increased unconjugated bilirubin due to decreased expression of UDPGT enzyme. Signup and view all the answers

In cases of mechanical RBC damage, what is a potential cause and its effect on red blood cell integrity?

Prosthetic heart valves can cause mechanical RBC damage, leading to hemolysis. Signup and view all the answers

What are the major reasons for jaundice in patients with cirrhosis?

Jaundice in cirrhosis is caused by shunting of blood past the liver, impaired conjugation ability due to hepatocellular dysfunction, and obstruction. Signup and view all the answers

Explain the role of portal hypertension in the development of varices in cirrhosis.

Portal hypertension causes the formation of thin-walled varices at systemic-portal anastomotic sites, which can bleed if traumatized. Signup and view all the answers

How does cirrhosis lead to a bleeding tendency in patients?

Cirrhosis leads to a bleeding tendency due to impaired synthesis of clotting factors, vitamin K deficiency, and thrombocytopenia from hypersplenism. Signup and view all the answers

What are some endocrine changes associated with cirrhosis, particularly related to estrogen metabolism?

In cirrhosis, there is a failure to conjugate estrogens, which can lead to changes in hormone levels and potential complications. Signup and view all the answers

Identify the primary causes of anemia in patients with cirrhosis.

Anemia in cirrhosis is primarily caused by disturbances in vitamin B12 and folate metabolism, bleeding, and hypersplenism. Signup and view all the answers

What are the potential outcomes of acute hepatitis?

Asymptomatic, acute hepatitis with resolution, recurrent severe acute hepatitis leading to liver failure, chronic hepatitis, and cirrhosis. Signup and view all the answers

Describe the laboratory findings typically seen during the early phase of acute hepatitis.

The early phase shows a hepatocellular injury pattern, increased unconjugated bilirubin, and marked rise in plasma transaminases. Signup and view all the answers

What happens to urobilinogen levels in urine during an obstructive phase of hepatitis?

Urobilinogen disappears from the urine, while the urine becomes positive for bilirubin. Signup and view all the answers

How do transaminase levels change in cases of alcoholic liver disease?

In severe alcoholic liver disease, transaminases, especially AST, are significantly elevated, often resulting in an AST:ALT ratio greater than 1. Signup and view all the answers

Define non-alcoholic fatty liver disease (NAFLD) and its types.

NAFLD is hepatic steatosis after excluding alcohol and other causes, with types being non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH). Signup and view all the answers

What biochemical marker is commonly raised in alcoholic liver disease and why?

GGT is commonly raised due to enzyme induction and cholestasis, indicating alcohol use and liver stress. Signup and view all the answers

What characterizes the hepatocellular injury pattern observed in acute hepatitis?

It is characterized by a marked rise in plasma transaminases, reflecting significant liver cell damage. Signup and view all the answers

How do immunoglobulins change during acute hepatitis?

There is an early increase in IgM followed by an increase in IgG. Signup and view all the answers

Study Notes

Liver Anatomy and Blood Supply

Hepatic artery provides 500 ml/min of oxygenated blood at 100 mm Hg.
Portal vein delivers 1000 ml/min of non-oxygenated blood at 10 mm Hg.
Hepatic vein serves as venous drainage, with pressure of 5 mm Hg.

Liver Architecture

Hepatic lobule: Hexagonal structural unit surrounded by connective tissue septae, containing portal tracts that house branches of hepatic arteriole, portal venule, and bile ductule. Central vein of lobule receives blood from surrounding sinusoids.
Hepatic acinus: Functional unit of liver, situated between two centrilobular venules, with blood flow from portal tract through sinusoids to centrilobular venule. Divided into three zones:
- Zone I: Periportal, high O2, involves oxidative metabolism.
- Zone II: Mediolobular.
- Zone III: Centrilobular, low O2, involved in CYP450 drug metabolism.

Bilirubin Metabolism

Begins with breakdown of hemoglobin in spleen macrophages: Hemoglobin → Hemin → Biliverdin → Bilirubin.
Transport: Unconjugated bilirubin is hydrophobic, bound to albumin, reaches the liver where it is conjugated with glucuronic acid via UDPDT enzymes to form BMG and BDG (water-soluble).
Excretion: Conjugated bilirubin moves to bile canaliculi, secreted into the GIT, transforms into urobilinogen in the colon, contributing to urine (present unless obstructed).

Bile Acid Production

Primary bile acids (cholic acid, chenodeoxycholic acid) are synthesized from cholesterol in the liver and conjugated with glycine/taurine for solubility.
Bacterial action in the GIT produces secondary bile acids (deoxycholic acid, lithocholic acid).
Enterohepatic circulation allows 75% reabsorption of bile acids, aiding in fat absorption and cholesterol solubilization.

Circulating Bile Acids

Normal circulation occurs post-meal as bile is secreted into the GIT; bile acids absorbed enter the blood and return to the liver.
Abnormalities, such as in hemolytic anemias, lead to increased unconjugated bilirubin, normal conjugated bilirubin, negative urine bilirubin, and increased urine urobilinogen.

Jaundice and Cholestasis

Post-hepatic jaundice occurs due to obstruction (e.g., gallstones, bile duct carcinoma); features include jaundice, dark urine, pale stools, and increased conjugated bilirubin in serum/urine.
Intra-hepatic jaundice can arise from inherited metabolism defects (e.g., Gilbert’s syndrome), causing mild increases in unconjugated bilirubin.

Acute Hepatitis

Results in hepatocellular injury reflected by increased unconjugated and later, conjugated bilirubin. Early urine reveals increased urobilinogen; during obstruction, urine is positive for bilirubin.
Plasma markers show early elevated transaminases, especially AST relative to ALT during significant liver damage.

Alcoholic Liver Disease

Ranges from fatty liver to cirrhosis, characterized by elevated GGT levels, and in severe cases, AST:ALT ratio greater than 1 due to AST predominance.

Non-Alcoholic Fatty Liver Disease (NAFLD)

Classified into NAFL (steatosis without inflammation) and NASH (inflammation present); risk factors include obesity and type 2 diabetes.
Diagnosis via non-invasive imaging; treatment focuses on lifestyle alterations.

Cirrhosis

Represents end-stage chronic liver diseases characterized by fibrosis, portal hypertension, with common etiologies including chronic viral hepatitis, alcoholic liver disease, and metabolic disorders.
Symptoms of decompensated cirrhosis include jaundice, dark urine, and fluid build-up; complications arise from portal hypertension, leading to varices and bleeding tendency.

Pathophysiology of Cirrhosis Complications

Jaundice results from shunting and impaired conjugation, showing mixed bilirubin elevation.
Ascites stems from portal hypertension, low albumin, and hyperaldosteronism.
Variceal bleeding occurs due to portal pressure effects, most commonly at esophageal sites.
Anaemia correlates to nutrient deficiencies, bleeding, and hypersplenism.
Endocrine changes due to inadequate estrogen conjugation; malnutrition features can also emerge from alcohol use, appetite loss, and malabsorption.

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Description

Explore the intricate structures of liver anatomy and its functional components in this quiz on chemical pathology. Understand the roles of the hepatic artery, portal vein, and hepatic lobule in maintaining liver function. Get ready to test your knowledge on liver architecture and its significance in health and disease.