Transcript CLINICAL CHEMIISTRY (MT 305) CARBOHYDRATE LECTURE ONE

CLINICAL CHEMISTRY-2 (MLT 302)
LIVER FUNCTION AND THE
BILIARY TRACT
LECTURE ONE
Dr. Essam H. Aljiffri
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 Introduction
 Normal hepatic function
Carbohydrate metabolism
Amino acid and protein metabolism
Lipid metabolism
Bile acid metabolism
Conjugation and detoxification
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• Assessment of hepatic function
Bilirubin metabolism
Jaundice
• Neonatal jaundice
Congenital defects in bilirubin transport
Serum enzymes in liver disease
Plasma proteins in liver disease
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• Liver diseases
Acute viral hepatitis
Chronic viral hepatitis
Hepatic cirrhosis
Hepatocellular and acute(fulminant) hepatic failure
Hepatic malignancy
Toxic liver damage
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 Gallstones
 Investigation of liver disease
Case histories
Case 1
Case 2
Case 3
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Introduction
• The liver plays a key role in the
intermediary metabolism of carbohydrates
and fats.
• The major organ of detoxification and
excretion of lipid-soluble substances,
including the major metabolite of haem
metabolism, bilirubin.
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Introduction
• Other roles include the synthesis of
plasma proteins which have a variety of
functions.
• Bile acids, necessary for fat digestion and
absorption, are also synthesized and
excreted by the liver.
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Structure of the Liver
- The liver contains two major cell types,
hepatocytes or parenchymal cells which
comprise about 60% of the liver, and
Kupffer cells which form part of the
reticuendothelial network and comprise
approximately 30% of the liver mass.
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-
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Normal Hepatic Function
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Normal Hepatic Function
- Carbohydrate Metabolism
• Hepatic glucose output maintains blood sugar
levels between meals, the principal sources of
glucose being hepatic glycogen (glycogenolysis)
and gluconeogenesis (from lactate, alanine and
glycerol).
• The liver also converts galactose and fructose to
glucose.
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Normal Hepatic Function
Amino Acid Metabolism
• Amino acids derived from the diet and the
breakdown of tissue proteins are transported to
the liver.
• Some are transaminated or deaminated to ketoacids, while others are metabolized to urea and
ammonia.
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Normal Hepatic Function
Amino Acid Metabolism
• The liver also synthesizes most proteins found in
plasma, except the immunoglobulins which are
produced by lymphoid tissue.
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Proteins measured in the
investigation of disease
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Normal Hepatic Function
Lipid Metabolism
•The liver plays an active role in lipid metabolism,
it removes chylomicron remnants from the
circulation and synthesizes very-low-density
lipoproteins (VLDL).
•Intermediate-density lipoprotein (IDL) is
converted to low-density lipoprotein (LDL) by
hepatic lipase and there is a high density of LDL
receptors on hepatocytes
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Normal Hepatic Function
Lipid Metabolism
• Precursor particles of HDL are synthesized in the liver,
as is lecithin cholesterol acyl transferase (LCAT), the
enzyme which converts precursor to functional HDL
particles.
• Further hepatic roles in lipid metabolism include the
production of ketone bodies from non-esterified fatty
acids (NEFA), cholesterol excretion into bile and
hydroxylation of vitamin D to form 25hydroxycholecalciferol.
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Normal Hepatic Function
Bile Acid Metabolism
•The primary bile acids are cholic acid and
chenodeoxycholic acid which are synthesized only
in the liver, from cholesterol.
•They are secreted in bile and most are
reabsorbed through enterohepatic circulation,
hepatic synthesis of bile acids being regulated by
the amount returning to the liver.
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Normal Hepatic Function
Bile Acid Metabolism
• Gut bacteria dehydroxylate the primary bile
acids producing the secondary acids,
deoxycholic and lithocholic acids.
• Deoxycholic acid is reabasorbed and enters the
enterohepatic circulation, while most lithocholic
acid is excreted in the stools.
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Bile Acid Metabolism
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Normal Hepatic Function
Conjugation and Detoxification
• Bilirubin conjugation and excretion, and other
substances metabolized and excreted by the
liver include steroid hormones and drugs.
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