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

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

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

4. 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

5. 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

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

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

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

9. 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

10. Bilirubin Metabolism

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. Storage
Glycogen
Vitamins
Iron
Blood

18. Immunologic
Phagocytosis of bacteria
IgA secretion

19. References
Biofortified. (2012). Retrieved from
Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins.
Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson .