LIVER AND BILIARY SYSTEM
D R A N I L C H A U D H A R Y
A S S O C I A T E P R O F E S S O R
P H Y S I O L O G Y
The small intestine receives not only chyme from the stomach but also secretions from the liver and pancreas.
LIVER
LocationR. HypochondriumEpigastric region
4 LobesLeft QuadrateCaudateRight
Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein
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LIVER
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The Liver
has tremendous variety of functions, including the secretion of bile for digestive purposes. -Largest Gland of
Body
-Wt.1200-1600gms
STRUCTURE OF LIVER
Liver largest internal organ.Hepatocytes form hepatic plates that are 1–2 cells thick.Arranged into functional units called lobules.each with diameter of 0.5 to 2 mm.
Plates separated by sinusoids.More permeable than other capillaries.
Contains phagocytic Kupffer cells.Secretes bile into bile canaliculi, which are
drained by bile ducts.
MICROSCOPIC ANATOMY
Hepatic lobules – tiny cylinders make up interior of liver; functional units of liver
Lobule – central vein; surrounded by radiating sheets of cuboidal cells – hepatocytes
Between plates of hepatocytes – blood filled channels – hepatic sinusoids
Blood filtering between hepatocytes comes from intestines
Sinusoids – Kupffer cells – hepatic macrophages; removes bacteria & debris from blood
Hepatocytes secret bile into the bile canaliculi and bile ductules.
bile ductule
STRUCTURE OF LIVER (CONTINUED)
Insert fig. 18.20
LIVER HISTOLOGY
Figure 24–20
Liver lobule is the basic functional units of the liverEach lobe is divided:
by connective tissueinto about 100,000 liver lobulesabout 1 mm diameter each
Dual blood supply
Hepatic portal vein Direct input from small
intestineHepatic artery/vein
Direct links to heart
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LIVER
HEPATIC BLOOD SUPPLY
1/3 of blood supply:arterial blood from hepatic artery proper2/3 venous blood from hepatic portal
vein, originating at:esophagusstomachsmall intestinemost of large intestine Hepatocytes are liver cellsAdjust circulating levels of nutrients:through selective absorption and secretion Blood Leaving the Liver returns to
systemic circuitVia hepatic veins:which open into inferior vena cava
MICROSCOPIC ANATOMY OF THE LIVER
THE PATHS OF BLOOD AND BILE IN HEPATIC LOBULE
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HEPATOCYTES
In a liver lobule form a series of irregular plates arranged like wheel spokes
Blood enters liver sinusoids: from small branches of hepatic portal vein from hepatic artery proper
As blood flows through sinusoids:hepatocytes absorb solutes from plasmaand secrete materials such as plasma proteins
Hepatic triad – 3 or more lobules meet ; contains 2 blood vessels and 1 bile duct
After filtering thru sinusoids blood collects in central vein
Flows into L & R hepatic veins and enters inferior vena cava
Bile canaliculi - narrow channels between sheets of hepatocytes ; liver secretes bile here
Bile passes into bile ductules of triads & into R & L hepatic ducts
Hepatic ducts merge Common hepatic duct
Common hepatic duct + Cystic duct from gallbladder join Bile duct
Bile duct joins Pancreatic duct at Hepatopancreatic ampulla and enters duodenum
Hepatopancreatic sphincter regulates passage of bile and pancreatic juices into duodenum
Bile ductules hepatic ducts common hepatic duct
cystic duct
common hepatic duct
gallbladder
common bile duct
hepatopancreatic sphincter
pancreas
duodenum
FUNCTIONS OF THE LIVER
Bile production: 600-1000 mL/day. Bile salts (bilirubin), cholesterol, fats, fat-soluble hormones, lecithin
Neutralizes and dilutes stomach acid Bile salts emulsify fats. Most are reabsorbed in the ileum. Secretin (from the duodenum) stimulates bile secretions, increasing water
and bicarbonate ion content of the bileStorage Glycogen, fat, vitamins, copper and iron. Hepatic portal blood comes to liver
from small intestine.Nutrient interconversion Amino acids to energy producing compounds Hydroxylation of vitamin D. Vitamin D then travels to kidney where it is
hydroxylated again into its active formDetoxification Hepatocytes remove ammonia and convert to ureaPhagocytosis Kupffer cells phagocytize worn-out & dying red & white blood cells, some
bacteriaSynthesis Albumins, fibrinogen, globulins, heparin, clotting factors
Detoxifies/removes Drugs Alcohol
Stores Gycolgen Vitamins (A, D, E, K) Fe and other minerals Cholesterol
Activates vitamin D Fetal RBC production Phagocytosis Metabolizes absorbed food
molecules Carbohydrates Proteins Lipids
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LIVER
DETOXIFICATION OF THE BLOOD
Liver can remove hormones, drugs, and other biologically active molecules from the blood by:
Excretion into the bile.Phagocytosis by Kupffer cells.Chemical alteration of the molecules.
Ammonia is produced by deamination of amino acids in the liver.
Liver converts it into urea. Excreted in urine.
DETOXIFICATION OF THE BLOOD (CONTINUED)
Inactivation of steroid hormones and drugs. Conjugation of steroid hormones and xenobiotics make them anionic.
Can be transported into bile by multispecific organic anion transport carriers.
Steroid and xenobiotic receptors stimulate production of cytochrome P450 enzymes.
SECRETION OF GLUCOSE, TRIGLYCERIDES AND KETONES
Liver helps regulate blood glucose concentration by: Glycogenesis and lipogenesis. Glycogenolysis and gluconeogenesis.
Contains enzymes required to convert free fatty acids into ketone bodies.
PRODUCTION OF PLASMA PROTEINS
Albumin and most of the plasma globulins (except gama globulins) are produced by the liver.
Albumin:Constitutes 70% of the total plasma protein.
Contributes most to the colloidal osmotic pressure in the blood.
Globulins:Transport cholesterol and hormones.
Produce blood clotting factors I, II, III, V, VII, IX, XI.
LIVER FUNCTIONS
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• produces glycogen from glucose• breaks down glycogen into glucose• converts noncarbohydrates to glucose• oxidizes fatty acids• synthesizes lipoproteins, phospholipids, and cholesterol• converts carbohydrates and proteins into fats• deaminates amino acids • forms urea• synthesizes plasma proteins• converts some amino acids to other amino acids• stores glycogen, vitamins A,D, B12, iron, and blood• phagocytosis of worn out RBCs and foreign substances• removes toxins from blood• produces and secretes
CLINICAL APPLICATION
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Hepatitis
• inflammation of the liver• most commonly caused by viral infection• can be caused by reactions to drug, alcoholism or autoimmunity
Signs and Symptoms• headache • low fever• fatigue • vomiting• rash• foamy urine• pale feces• jaundice • pain
Hepatitis A – not washing hands or eating raw shellfishHepatitis B – chronic; serumHepatitis C – serumHepatitis D – very severe; only produces symptoms if infected with B; serumHepatitis E, F, G – more rare