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The normal Liver
Anatomy of the Liver (Click Here)
2. The Vessels
of the Liver (Click Here)
Anatomy of the Liver (Click Here)
of the Liver (Click Here)
1. Gross Anatomy of the liver:
liver is wedge-shaped, and covered by a network of
connective tissue (Glisson's capsule).
- It is
located in the upper right region of the abdominal
liver is divided into two main lobes by the falciform
ligament, which is a mesentery attached to the anterior
right lobe is six times larger than the left lobe.
right lobe is situated over the right kidney.
left lobe lies over the stomach.
liver has the remarkable property of self-regeneration.
If a part of the liver is removed, the remaining parts
can regrow back to its original size and shape.
The Vessels of
artery: a blood vessel which supplies the liver with
oxygenated arterial blood flow to the liver. It supplies
20% of the liver's blood.
portal vein: a blood vessel which drains venous blood
into the liver from the entire gastrointestinal
supplies the remaining 80% of the liver's blood.
vein: a blood vessel which drains blood from the
liver into the inferior vena
duct: channels through which bile secreted by
the hepatocytes drain into.
Bile in the bile ducts then drain into the left and right
bile duct: the duct formed after the left and right
hepatic ducts converge with the cystic duct from the gallbladder.
3. Microscopic Anatomy of the Liver:
- Hepatocytes: a.k.a. liver
the hexagonally shaped functional units of the liver,
made up of hepatocytes arranged in one-cell-thick
platelike layers that radiate from the central vein to the edge
of the lobule.
area: situated at he corner of each lobule, it is a
complex composed of branches of the hepatic portal vein,
hepatic artery, bile duct, and nerve.
delicate blood channels between the radiating rows of
hepatocytes which transport blood from the branches of
the hepatic portal vein and hepatic artery from the
portal areas to the central vein.
canaliculi: channels through which bile secreted by
hepatocytes drain into the bile ducts in the portal
- Central vein: a blood vessel
in the middle of each lobule which receives blood from
the hepatic portal vein and hepatic artery via the
sinusoids and drains the blood into the hepatic vein.
4. Functions of the Liver:
is estimated that the liver carries out several hundred
separate functions involving thousands of different
liver and the kidney are the major organs responsible for
regulating the steady state of blood metabolites and the
composition of blood tissues.
food materials absorbed from the gastrointestinal tract
pass directly into the liver where they are stored or
converted into some other form as required by the body at
optimun level of glucose in a person's blood is
approximately 90 mg of glucose per 100cm3 of
liver prevents the blood glucose level from fluctuating
too much and so prevents damage to tissues that cannot
store glucose, such as the brain.
- All hexose
sugars, including galactose and fructose
are converted into glucose in the liver and stored as the
insoluble polysaccharide, glycogen.
blood glucose level drops below 60 mg cm-3 ,
the pancreas will
secrete glucagon, which
stimulates the liver to undergo glycogenolysis to restore
the blood glucose level back to optimum level.
blood glucose level exceeds 90 mg cm-3,such as
after a carbohydrate-rich meal, the pancreas will secrete
stimulates the liver to undergo glycogenesis to bring
the blood glucose level down to its optimum level.
the demand for glucose has exhausted the glycogen store
in the liver, the liver undergoes gluconeogenesis to obtain
in the body which cannot be utilized or stored as
glycogen are converted into fats and stored.
body is unable to store absorbed amino acids, and those
not immediately required for protein synthesis
or gluconeogenesis are deaminated in the liver.
the enzymatic removal of
the amino group (-NH2) from the amino acid
with the simultaneous oxidation of the
reminder of the molecule to form a carbohydrate which is
utilized in respiration.
nitrogenous product of deamination is ammonia (NH3).
is toxic and dangerous if accumulated in large amounts.
The ammonia produced by deamination is converted in the
liver into the soluble excretory product urea via the
liver is also able to produce some amino acids which are
deficient in the diet via transamination, e.g. glutamic
the synthesis of amino acids by the enzymatic transfer of
the amino group from an amino acid to a carbohydrate in
the form of a keto acid.
Plasma Protein production:
majority of plasma proteins
are synthesized in the liver. The most common being
- Plasma globulins are also
plasma proteins are blood-clotting factors, prothrombin,
liver is involved in the processing and transport of fats
rather than their storage.
liver converts excess carbohydrates to fat,
cholesterol and phospholipids
from the blood and breaks them down,
and synthesizing them if necessary.
Vitamins and Mineral storage:
liver stores mainly the fat-soluble vitamins, like
vitamins A, D, E, and K.
such as copper, zinc, cobalt,molybdenum, iron and
potassium are also stored in the liver.
of the iron in the liver comes from the breakdown of old erythrocytes and is
stored as ferritin in the
liver for later use in the formation of new erythrocytes
in the bone marrow.
Formation of Erythrocytes in foetus:
foetal liver is responsible for the initial formation of
erythrocytes until this function is gradually taken over
by the bone marrow.
Breakdown of Erythrocytes in adults:
adult liver takes on the opposing role of breaking down
old erythrocytes and haemoglobin.
erythrocytes are broken down by phagocytic macrophage
cells in the liver.
is broken down into haem and globin.
globin is reduced to its constituent amino acids and is
used according to demand.
is eventually converted into iron and bilirubin, which is
a yellow component of bile.
- Bile is a viscous, greenish
yellow fluid secreted by hepatocytes.
- It is
involved in digestion, the absorption of fats and is a
means of excretion of bile pigments.
bile pigments have no function and their presence is
is made up of bile salts, which are derivatives of
cholesterol, synthesized in hepatocytes. The most common
bile salts are sodium glycocholate and sodium
taurocholate. They are secreted with cholesterol and
phospholipids as micelles.
bile micelles exist as small droplets of lipids, because
cholesterol and phospholipids hold the bile pigments
together so that all the hydrophobic ends of the
molecules are orientated in the same way.
small droplets greatly increases the surface area for
pancreatic lipase to convert
lipids into glycerol and fatty acids, so these
can then be absorbed from the gut.
liver is the first major organ which encounters toxins
from the gastrointestinal tract.
major toxic substance in the blood is ammonia.
are rendered harmless by oxidation, reduction, methylation, or by
combining molecules together.
detoxified substances are then excreted by the kidney.
popular analgesic, paracetamol, if taken in excess is
changed into a substance which affects enzyme systems and
can cause damage to the liver and other tissues.
Hwa Chong Junior College, 1996, Biology lecture on
Dr Sing Kong Yuen
1997 ASIA USA
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