Biliary System

Dr. Mahvash Khan

Biliary System

Includes  Liver   Gallbladder Ducts

 Liver is the largest organ in the body  Liver Has Very High Lymph Flow (half of the lymph formed in the body under resting conditions)  Liver Has High Blood Flow and Low Vascular Resistance (1350 ml/min) (27% of the cardiac output)  The basic functional unit of liver is the “liver lobule”(50,000-1000,000)

Blood Supply of Liver

 Sources (Two)    Hepatic Artery Hepatic Portal Vein Blood is drained into Hepatic Vein which joins inferior venacava

Physiologic Anatomy of Liver

 Functional Units (Lobules)     Hexagonal Arrangement of Tissues around central Vein Branch of Hepatic Artery, Hepatic portal vein and a bile duct at the outer edge of Lobule

Functions of liver

         Metabolic Functions Synthetic Functions Storage Functions Blood reservoir Hemopoietic Function Blood Cleansing Function Activation of Vitamin-D Excretory Functions Digestive Function

Functions of liver- Metabolic Functions

  Carbohydrate Metabolism  Blood Glucose Buffer system     Storage of Glycogen Conversion of Galactose & Fructose to Glucose Gluconeogenesis Formation of Many chemical compounds from intermediate products of Carbohydrate metabolism Protein Metabolism  Deamination of Aminoacids     Formation of Urea Synthesis of Plasma Proteins Synthesis of Clotting Factors Interconversion of Various Amino acids

Functions of liver- Metabolic Functions (Con’d)  Fat Metabolism    Oxidation of Fatty acids to supply energy Synthesis of cholesterol, phospholipids & lipoproteins Synthesis of fat from proteins & carbohydrates

Functions of liver- Synthetic Functions

   Synthesis of plasma proteins Synthesis of clotting factors (factor VII, IX, X, prothrombin, fibrinogen) Synthesis of various proteins required for the transport of Steroid & Thyroid Hormones

Functions of liver- Storage Functions

 Storage of:     Iron Copper Glycogen Vitamins (A,D,B12)

Functions of liver- Blood reservoir & Hemopoietic Function  Blood Reservoir (Blood sinusoids-dilated capillaries)  Hemopoietic Function  In fetal life

Functions of liver- Blood Cleansing Function    Removal of bacteria (by Kupfer cells) Detoxification of drugs & chemicals (like penicillin, sulfonamides) Removal of old red blood cells

Functions of liver-

Activation of Vitamin-D

 Formation of 25 hydroxycholecalciferol

Functions of liver-

Excretory Functions

    Excretion of calcium through gut Excretion of bilirubin Excretion of cholesterol Excretion of hormones

Functions of liver- Digestive

Functions

 Role of Bile salts in digestion & Absorption of fats

Bile Secretion by Liver

 Bile is secreted by Liver  Normally between 600 and 1000 ml/day  Bile is secreted in two stages

 Bile plays an important role in fat digestion and absorption  Bile serves as a means for excretion of several waste products from the blood such as

bilirubin

, (end product of hemoglobin destruction), excess

cholesterol

, certain hormones etc

Composition of Bile

Water Bile salts Bilirubin Cholesterol Fatty Acids Lecithin Na+ K+ Ca++ Cl HCO 3 Liver Bile 97.5 g/dl 1.1 g/dl 0.04 g/dl 0.1 g/dl 0.12 g/dl 0.04 g/dl 145 mEq/l 5 mEq/l 5 mEq/l 100 mEq/l 28 mEq/l Gallbladder Bile 92 g/dl 6 g/dl 0.3 g/dl 0.3-0.9 g/dl 0.3-1.2 g/dl 0.3 g/dl 130 mEq/l 12 mEq/l 23 mEq/l 25 mEq/l 10 mEq/l

Secretion of Bile by liver

      250 ml to 1 liter per day Continuous secretion by hepatocytes Aqueous alkaline fluid Important organic constituent  Bilirubin   Cholesterol Lecithin  Bile salts Taken by common bile duct to the duodenum Enterohepatic circulation

Bile Salts

    Derivatives of Cholesterol    Cholic acid & Chenodeoxycholic acid Conjugation with glycine & taurine Sodium salts of conjugated acids Average amount 3 to 4 gms in the body Only 5% excreted in faeces Powerful choleretics

Stimulus for Bile secretion

   Chemical Mechanism  Bile Salts Hormonal Mechanism  Secretin Neural Mechanism  Vagalstimulation

Gallbladder

  Site   Sac like structure Located beneath the liver Functions   Storage of bile Concentration of bile

Gallbladder Functions: Storage of bile

  Can store 450 ml of bile (12 hr of secretion) Transported to the Gallbladder between the meals

Gallbladder Functions: Concentration of bile    Active transport of salts Water following osmotically Concentration of bile 5 to 10 times

Gallbladder : Emptying of Gallbladder     Relaxation of sphincter of ODDI Contraction of gallbladder Role of cholecystokinin Stimulation by fatty foods in duodenum

Gallbladder : Formation of Gall stones     Common site of formation of stones 75% of stones made of cholesterol 25% made of bilirubin In case of Gallbladder removal bile is stored in common bile duct which becomes dilated