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Function and illness
The liver: how it functions and how it becomes ill
The liver is an organ which has among the most complex and in some ways mysterious functions within the human body. A single organ, (many are double, for example the kidneys and the lungs), the 1500 gram liver is the largest gland of the body. (Fig.1). It receives arterial blood rich in oxygen by means of the hepatic artery as well as venous blood via the portal vein which collects the blood coming from the digestive apparatus and from the spleen, rich in nutritive substances.; all the blood coming out of the liver reaches the supra-hepatic veins which immediately open into the inferior vena cava and thence into the right hand side of the heart.
The bile capillaries are also located in the liver: these collect the bile produced by the hepatic cells, which is conveyed by means of small ducts located in the liver (biliary canals) into ever larger ducts until the main hepatic duct, and from this into the intestine. Communicating with the main hepatic duct is the cystic duct which allows the inflow and outflow of bile from the gall bladder, an approximately pear shaped formation located immediately below the lower side of the liver (Fig.1).
Strategically located in the right upper part of the abdomen, the fundamental job of the liver is to drain the blood coming from the intestine, capturing the nutritive substances (derived from diet) which it contains, metabolising them and distributing them amongst the other organs.
In essence, it is the chemical laboratory of our body.
It should be remembered more often, as in the more than 5000 year old Chinese medicine, that the liver as the most important organ for the use and distribution of the “energy” which the kidney dispenses. In addition to the good substances, our body quite regularly receives harmful substances (pharmaceuticals, environmental toxins and food additives). All this rubbish is mainly removed by complex chemical reactions of the liver which convert it to water soluble compounds which are then eliminated via the kidneys and/or the intestine.
Looking at the environmental toxins (mainly in food) of a man who lived in medieval times, it is easy to understand how they are profoundly different from those to which we are exposed today. Hence, the liver of our ancestors was as eminently capable of carrying out its functions as is the liver of today, indicating the plasticity and ductility of the organ, and (in general in man) its ability to adapt to the world in which it finds itself.
From a
functional point of view, the elementary and essential structure of the liver
is the hepatic cell (hepatocyte).
This obtains numerous substances
from the blood, whether arterial or portal, transforms them by means of its
complex cellular structure and returns them once elaborated to the blood
or the bile; in effect, the liver is the most important and irreplaceable
organ in the maintenance of chemical equilibrium and organism function.
Amongst the various biological functions carried out by this organ, the most important are:
A) Metabolic function
B) Detoxifying function
C) Production of bile
Metabolic function: the group of complex biochemical activities which
take place in the liver are defined as “metabolic function”.
In practice, the organ intervenes in the most part of the metabolism of the
biochemical constituents of the organism; in particular, its function is
determinant for the metabolism of:
- Proteins: a major part of the proteic substances of the blood is produced in the liver; because of their importance, albumin and coagulation factors are mentioned.
- Sugars: sugars (carbohydrates) are almost entirely synthesised in the liver; the principal sugar, glucose, may be stored in the hepatocytes in the form of glycogen, and then released into the blood when it is needed for energy.
- Fats: alimentaryfats (lipids) absorbed by the intestine and those coming from fatty tissue deposits, may be utilised, transformed and partly eliminated by the liver; of particular importance are triglycerides and cholesterol.
- Vitamins: the most important are those of the B complex (B, - B, - Bl 2), vitamin K (fundamental for the blood coagulation process) and the liposoluble vitamins (A-D-E); in order to carry out their function, most vitamins must first be metabolised in the liver.
- Hormones. The liver influences the metabolism of the hormones produced by various glands within the organism; in fact, it produces the proteins necessary for hormone transport in the blood and can modulate their activity, activating or inactivating the hormone
Detoxifying function: the detoxifying action of the liver on various
substances which are dangerous for the organism may be explained in terms of
complex chemical activities, which can alter the various original substances
and also bind them to other substances which behave as transporters; thus transformed,
numerous substances which would be harmful, may be more easily eliminated in
the bile or by means of other organs ( e.g. kidneys).
In addition, these same biochemical processes are also used to metabolise
many pharmaceuticals: in particular since the majority of these are re-elaborated
at the hepatic level, sometimes certain pharmaceuticals can become harmful
to the hepatic cells, causing damage which can even be seriously dangerous.
Production of bile: bile is an aqueous solution produced by the hepatic
cells whose principal function is to allow the intestinal absorption of nutritional
fats and lipo-soluble vitamins (A-D-E-K).
Bile also has other important functions; amongst these, it must be remembered
that bile is the main means by which not only numerous toxic substances and
pharmaceuticals but also excess cholesterol are eliminated. In addition,
also the bilirubin (a substance which remains after the destruction of red
blood cells) is for the most part excreted in bile, determining its characteristic
colour; therefore, changes in liver function can diminish the organ’s
ability to capture, transform and eliminate the bilirubin, its subsequent increase
in concentration in the blood causing the typical yellowing of the eyes and
skin (jaundice), characteristic of many hepatic and/or biliary illnesses.
Unfortunately, this perfect worker can get sick much more often than we might
imagine.
Its size is such that only about 30% of the liver is necessary to carry out
all of its required functions.
As a result, the first symptoms of liver disease
begin to manifest themselves only when more than 70% of the hepatic cells
have been damaged in some way, something which takes time.
Furthermore, the liver is the only organ of our body which regenerates, i.e.
just like a lizard’s tail, it can re-grow. Unfortunately however, especially
when the harmful factors which attack the liver do so in a constant and chronic
manner, without giving any alarm signals, which is sadly what happens most
frequently, liver re-growth may be anomalous and result in large scars which
upset the entire liver anatomy and circulation, giving rise to what is known
as cirrhosis (see Fig.2).
The main factors which are damaging to the liver or hepato-detrimental in technical terms, are:
- Infectious agents (e.g. viruses, bacteria, parasites), mainly the viruses which are usually indicated with letters of the alphabet (A, B, C, D, E, F, G);
- Toxic substances (e.g. pharmaceuticals, alcohol, chemical substances);
- Pathologies of other organs (e.g. cardiopathies, metabolic illnesses, tumours).
In Italy the most important factors among all these are the viral infections
(above all the C virus) and alcohol, both for their frequency and the seriousness
of the damage they cause.
One study carried out by the Foundation for the Study of Liver Disease (the
Dionysos Project), carried out at Campogalliano (Modena province) at Cormons
(Gorizia province) has led to the discovery that some 20% of the general
Italian population have symptoms and/or signs (the famous reduced transaminases
!) of hepatic damage, fortunately moderate. Luckily this is due only in a small
part to the C virus and alcohol abuse, but mainly arises from bad eating
habits and the consumption of foods which are too fatty.
About 1% of the population
examined has a serious cirrhotic disease. This means that in a stadium with
50.000 spectators, approximately 500 are cirrhotic. If we then extrapolate
this to calculate the number of people in Italy
who suffer from cirrhosis, we get the number 600.000. This indicates that
liver disease is a real social problem in which investment is small and bad
in terms of prevention, diagnosis and research.
But fortunately, there are always exceptions.
In general terms, Italian clinical and experimental liver research is without doubt the leader in the European and international arenas, even though our researchers (young or otherwise) often find themselves having to fight Goliath with the classical sling.
And this is one of the reasons why our association, the Foundation for Liver Studies, has for the past 15 years, been financing clinical activities with liver patients and their relatives and more advanced basic research in the field of liver disease. The endeavours have been and are considerable, but the scientific and human satisfaction compensate abundantly.
The Foundation for Liver Studies has earned firm recognition clinically amongst patients and scientifically amongst the international community. This, thanks to the help of many people who have wished to donate their time and/or money to the Foundation. The commitment of each one of us is the real strength of our action.
Recently, our association has taken on the legal responsibility of
ONLUS, an unattractive-sounding acronym which indicates voluntary non-profit
organisations.
In the hope that someone reading this will be convinced to become one of
us, and making a date soon with a new article on everything about nutrition
and the liver, we invite you to contact us for any problem at our office
(Trieste: tel. 040-3994210).
Looking forwards to seeing you, and thanking you in advance!
Anatomical aspect of a normal liver.
Anatomical aspect of a liver affected by advanced cirrosis. 