Liver

PHYSIOLOGY

Overview of the Liver

  • The liver is a complex organ with vital functions for body health.

Anatomy of the Liver

  • Major Structures:

    • Inferior vena cava: Returns deoxygenated blood to the heart.

    • Aorta: Sends oxygen-rich blood to the body.

    • Hepatic veins: Drain blood from the liver.

    • Hepatic artery: Supplies oxygen-rich blood to the liver.

    • Hepatic portal vein: Carries nutrient-rich, oxygen-poor blood from the digestive organs to the liver.

    • Bile ducts: Transport bile from the liver to the gallbladder and small intestine.

Structure of Liver Lobule

  • Key Components of a Hepatic Lobule:

    • Hepatocytes: Main functional cells of the liver.

    • Central vein: Drains blood from the lobule into the hepatic vein.

    • Portal vein: Supplies nutrient-rich blood.

    • Bile duct: Collects bile produced by hepatocytes.

    • Hepatic artery: Supplies oxygen-rich blood directly to the lobule.

    • Hepatic venule: Drains blood from the portal vein.

    • Sinusoids: Specialized capillaries between hepatocytes that facilitate exchange of substances.

    • Bile canaliculi: Small channels that collect bile from hepatocytes.

    • Reticuloendothelial (Kupffer) cells: Macrophages that help in phagocytosis.

Functions of the Liver

  • The liver performs 500 vital functions related to:

    • Immunity against infection.

    • Protein and cholesterol synthesis.

    • Waste excretion via bile.

    • Blood clotting regulation.

    • Detoxification of drugs, chemicals, and alcohol.

    • Conversion of excess glucose into starch for storage.

    • Fat digestion support through bile production.

Detailed Functions

  • Endocrine Function:

    • Breakdown of hormones such as estrogens to prevent accumulation, linked to conditions such as gynecomastia in chronic liver disease.

    • Activation of Vitamin D for calcium absorption.

  • Clotting Function:

    • Production of key clotting factors like prothrombin and fibrinogen.

    • Production of bile salts that facilitate the absorption of Vitamin K, essential for blood clotting.

  • Protein Production:

    • Synthesis of plasma proteins including albumin and lipoproteins.

    • Albumin regulates water balance in blood and contributes to osmotic pressure.

  • Exocrine Function:

    • Bile production, crucial for fat digestion and absorption.

    • Secretion of bicarbonate to reduce acidity in the duodenum.

    • Excretion of bilirubin, which is formed from the degradation of hemoglobin in aged red blood cells.

  • Metabolic Function:

    • Conversion of glucose to glycogen for storage and later release as needed.

    • Urea production from excess ammonia during protein metabolism to prevent toxicity.

    • Involved in cholesterol metabolism and conversion into bile salts.

  • Detoxification Function:

    • Major organ for detoxification of drugs and poisons, modifying substances for excretion through urine or bile.

  • Reticuloendothelial Function:

    • Collaborates with the spleen for hemopoiesis, antibody production, and removal of old red blood cells through Kupffer cells.

Liver Function Tests (LFTs)

  • Common Tests include:

    1. Aspartate aminotransferase (AST)

    2. Alanine aminotransferase (ALT)

    3. Lactic acid

    4. Alkaline phosphatase

    5. Bilirubin levels

    6. Prothrombin time

    7. Albumin and globulins

Specific Tests Descriptions

  • Aspartate aminotransferase (AST):

    • Increase indicates cellular injury or death; found in liver, heart, muscle, kidneys, and measured for liver health.

  • Alanine aminotransferase (ALT):

    • Indicator of liver function; increases in conditions like hepatitis or cirrhosis.

  • Bilirubin:

    • Elevation result from excessive RBC destruction, liver malfunction, or duct blockage.

    • Direct (conjugated) bilirubin: Elevated in obstruction/hepatocellular disease.

    • Indirect (unconjugated) bilirubin: Elevated in hemolytic diseases.

  • Alkaline phosphatase:

    • Indicator of intra/extrahepatic obstruction, hepatic carcinoma, or cirrhosis.

  • Prothrombin time:

    • Indicates liver function and vitamin K status; increases with liver damage.

  • Albumin and globulins:

    • Chronic liver diseases show elevated gamma globulins.

  • Alpha Feto Protein (AFP):

    • Produced by liver in patients with hepatocellular carcinoma or metastatic liver disease.

Knowledge Evaluation

  • Which is NOT a function of the liver?

    • a. Production of glucagon (not produced by the liver)

    • b. Detoxification of the body of alcohol

    • c. Metabolizes nutrients

    • d. Bile production

  • True or False:

    • Alkaline phosphatase is not a good indicator of intra/extra hepatic obstruction.

  • Serum marker increase in hemolytic disease of the liver:

    • Alpha feto protein

    • Blood glucose levels

    • Bilirubin direct

    • Bilirubin indirect