9 Flashcards
Major Functions Of The Liver:
Performs > 500 chemical processes.
Produces > 160 different proteins.
Makes clotting factors for the blood.
Releases & stores sugar as glycogen.
So, it plays important functions in metabolism,
synthesis & detoxification.
Bile ………. forms bile, that is stored in the …………..
and is released into the …………….
Liver forms bile, that is stored in the gallbladder
and is released into the duodenum.
The most important constituents of bile are:
- Water. - Inorganic salts. - Bile acids, bile salts and bile pigments. - Phospholipids. - Cholesterol.
Bile salts and phospholipids ( function) ?
Without bile?
emulsify food lipids,
and activate lipases.
Without bile: Steatorrhea, fatty stool.
Reduced absorption of fat-soluble vitamins.
Bile secretion is primarily regulated by a
feedback mechanism, with hormonal & neural controls.
Hormonal control by: CCK, secretin. Parasympathetic & sympathetic innervations.
Bile Acids & Bile Salts formation?
Primary bile acids are those synthesized by the liver
& secondary bile acids result from bacterial actions
on the primary ones in the colon.
• Bile acids are conjugated with taurine or glycine (in
liver) bind with Sodium & Potassium bile salts,
as Na+ or K+ -taurocholic acid & -glycocholic acid.
The bile acid chenodeoxycholic acid is used in
the treatment of
gallstones
amphipathic molecule that can act like an
emulsifying agent & help solubilize cholesterol.
Degradation of Heme from?
About 85% of heme degraded from RBCs In reticuloendothelial system (RES), particularly in the liver & spleen.
& 15%
from turnover of immature RBCs & cytochromes.
Formation of Bilirubin:
The first step in heme degradation is catalyzed by the
“microsomal heme oxygenase system” of the RES, in
the presence of NADPH and O2.
Second oxidation by the same enzyme system results
in:
o→ cleavage of the porphyrin ring
o→ production of biliverdin (green pigment).
o→ release of ferric iron & CO.
Biliverdin is reduced → bilirubin (red-orange) by
biliverdin reductase.
• Bilirubin and its derivatives are termed bile pigments
Uptake & Conjugation of Bilirubin by the Liver :
Bilirubin dissociates from albumin & enters hepatocytes, where it binds to intracellular proteins, protein ligandin.
the solubility of bilirubin is increased by addition of two molecules of glucuronic acid → “conjugation”
Unconjugated bilirubin bonded to albumin in blood
is also called indirect bilirubin.
Secretion of Bilirubin Into Bile:
actively transported against a concentration
gradient into the bile canaliculi and then into
bile.
Formation of Urobilins In The Intestine:
Bilirubin diglucuronide is hydrolyzed and reduced
by intestinal bacteria producing urobilinogen, a
colorless compound.
Most of urobilinogen is oxidized by intestinal
bacteria to stercobilin, which gives feces its
characteristic brown color.
refers to the yellow color of
skin, nail beds and sclerae,
Jaundice
Called also icterus
caused by deposition
of bilirubin due to hyperbilirubinemia.
Types of Jaundice: classified into three major forms:
- Hemolytic jaundice.
- Hepatocellular jaundice.
- Obstructive jaundice.
Neonatal jaundice
Laboratory Investigations of Haemolytic Jaundice
Blood: • Increased blood unconjugated (indirect) bilirubin. Urine: • Increased urobilinogen.
• Normal color; (no bilirubin in urine, it is bound to
albumin).
Stool: • Dark color. • Increased stercobilin (produced from increased
urobilinogen)
