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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)
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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
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