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Page 1: Biliary System

Biliary System

Dr. Mahvash Khan

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Biliary SystemIncludes

Liver Gallbladder Ducts

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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)

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Blood Supply of Liver Sources (Two)

Hepatic Artery Hepatic Portal Vein Blood is drained into

Hepatic Vein which joins inferior venacava

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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

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

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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

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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

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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

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Functions of liver- Storage Functions Storage of:

Iron Copper Glycogen Vitamins (A,D,B12)

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Functions of liver- Blood reservoir & Hemopoietic Function Blood Reservoir (Blood sinusoids-dilated

capillaries)

Hemopoietic Function In fetal life

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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

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Functions of liver- Activation of Vitamin-D Formation of 25 hydroxycholecalciferol

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Functions of liver- Excretory Functions

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

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Functions of liver- Digestive Functions

Role of Bile salts in digestion & Absorption of fats

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

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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

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Composition of BileLiver Bile Gallbladder Bile

Water 97.5 g/dl 92 g/dl Bile salts 1.1 g/dl 6 g/dlBilirubin 0.04 g/dl 0.3 g/dlCholesterol 0.1 g/dl 0.3-0.9 g/dlFatty Acids 0.12 g/dl 0.3-1.2 g/dlLecithin 0.04 g/dl 0.3 g/dlNa+ 145 mEq/l 130 mEq/lK+ 5 mEq/l 12 mEq/lCa++ 5 mEq/l 23 mEq/lCl- 100 mEq/l 25 mEq/lHCO3- 28 mEq/l 10 mEq/l

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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

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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

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Stimulus for Bile secretion Chemical Mechanism

Bile Salts Hormonal Mechanism

Secretin Neural Mechanism

Vagalstimulation

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Gallbladder Site

Sac like structure Located beneath the liver

Functions Storage of bile Concentration of bile

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Gallbladder Functions: Storage of bile Can store 450 ml of bile (12 hr of

secretion) Transported to the Gallbladder between

the meals

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

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

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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