MLAB 2401: Clinical Chemistry Keri Brophy-Martinez Liver Anatomy and Physiology

Where is the Liver? Upper right quadrant, beneath the diaphragm Largest internal organ Weighs ~ 1500 grams

Anatomy of the Liver Consists of 2 lobes divided by falciform ligament There is no known difference between the lobes

Liver Vascular organ Hepatic artery Portal vein Supplies O2 rich blood from heart to liver Provides 20-30% of blood supply to liver Portal vein Supplies nutrient rich blood from the digestive tract Provides 70-80% of blood to liver From Aorta From GI tract

Microscopic Anatomy of the Liver Lobules make up the liver 6-sided structure Central vein with portal triads at each corner Triad contains a hepatic artery, portal vein and bile duct surrounded by connective tissue Function in metabolic and excretory actions

Microscopic Anatomy of Liver Cell types Hepatocytes 70% of volume of liver Regenerative Perform major functions of liver Kupffer cells Macrophages acting as phagocytes

Biochemical Function of the Liver Excretion/Secretion Synthesis Detoxification Storage Immunologic

Excretory System Excretion of bile acids, cholesterol, bilirubin Begins at the bile canaliculi, enters hepatic ducts, then to common hepatic & bile duct

Excretion/Secretion Liver processes and excretes Bile Water, electrolytes, phospholipids, bile salts or acids, bile pigments, cholesterol , heme waste products, and other substances from blood 3L produced/day 1L excreted/day Functions Bile acids needed for fat absorption Mechanism to remove cholesterol and waste Bilirubin is the principal pigment in bile

Bilirubin Metabolism

Metabolism of Bilirubin Around 126 days, RBCs are phagocytized and hgb released Hgb broken down into: Heme Converted to bilirubin Globin Broken into amino acids and recycled Iron Bound by transferrin and returned to iron stores in the liver or bone marrow

Metabolism of Bilirubin Bound by albumin and taken to liver (unconjugated or indirect bilirubin) Water insoluble Can not be removed from body Once at the liver, unconjugated bilirubin flows into sinusoidal tissue and albumin releases it Ligandin, picks up the unconjugated bilirubin and presents it to glucuronic acid In the liver it becomes conjugated with the help of UDP-glucuronyl transferase Water soluble Combines with gallbladder secretions and expelled into intestines

Metabolism of Bilirubin Intestinal bacteria degrade conjugated bilirubin to form urobilinogen 80% of urobilinogen formed is oxidized to stercobilin and excreted in feces, giving stool the brown color 20% of urobilinogen formed Absorbed by extrahepatic circulation to be recycled through liver and re-excreted Enters systemic circulation to be filtered by kidney and excreted in urine

Synthesis Synthesize many biological compounds Carbohydrates Metabolism important Uses glucose for its own cellular energy Circulates glucose to peripheral tissue Stores glucose as glycogen Major player in maintaining stable glucose concentration due to glycogenesis, glycogenolysis and gluconeogenesis

Synthesis Lipids Proteins Liver gathers free fatty acids from diet and breaks them down to Acetyl- CoA to form triglycerides, phospholipids or cholesterol Converts insoluble lipids to soluble forms 70% of cholesterol produced by the liver Proteins Almost all proteins made in the liver Exceptions are immunoglobulins and hgb

Detoxification Liver serves as a gatekeeper between the circulation and absorbed substances First pass: every substance absorbed in GI tract passes through liver Detoxification includes drugs and poisons, and metabolic products like ammonia, alcohol, and bilirubin 3 mechanisms Binds material reversibly to inactivate Chemically modify compound for excretion Drug metabolizer for detox of drugs and poisons

Storage Glycogen Vitamins Iron Blood

Immunologic Phagocytosis of bacteria IgA secretion

References Biofortified. (2012). Retrieved from http://www.biofortified.org/2010/03/glowing-phagocytosis/ Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins. http://www.livercancer.com/liver_anatomy.html Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson .