The pathogenesis of both acute and viral hepatitis is slowly being unravelled. Thus far, most data show that members of the hepadnaviridae family are not highly cytotoxic per se. It appears that the intense levels of cellular death are primarily due to host defence mechanisms against the HBV infection.
The virus is most efficiently transmitted through percutaneous introduction. Sexual transmission and perinatal transmission are less efficient, typically requiring high titres of virus. HBV is most concentrated in the liver and blood, with lesser amounts found in saliva and semen.
The
Liver
The liver plays a pivotal role in helping the body maintain
adequate levels of metabolites in the blood stream. The liver is also
important in detoxifying potentially toxic chemicals that may enter our
blood stream.
On average, the liver weighs about four pounds and is the only organ able to regenerate itself even when up to 25% of it is removed.
The liver has many functions involved in digestion and metabolite conversion. Some of its key functions are:
Bile Production:This
fluid is stored in the gallbladder for release when needed in digestion.
Bile is necessary for the digestion of fats as it dissolves fat down into
small globules. Bile works in the same way as detergent lifts oil off
greasy plates. Bile also assists in the absorption of fat soluble vitamins
(i.e. vitamin A, D, F, and K) In addition, bile converts beta-carotene
to vitamin A.
Glucose Homeostasis: Blood sugar levels must be maintained for
other organs to functions properly, especially the brain. The liver plays
a pivotal role in that it is one of the sites where excess sugar can be
stored in the form of glycogen (a polysaccharide) when there is an overabundance.
Glucose can then be released from the glycogen when needed by the body.
Fat Metabolism: The liver is involved in the synthesis of fatty
acids from amino acids and sugars, in the production of lipoproteins,
cholesterol, and phospholipids, and in the oxidation of fat to produce
energy. Excess food is converted to fat in the liver which is then transported
to the adipose (fatty) tissues of the body for longer-term storage.
Detoxification: Protein metabolism and bacterial fermentation of
food in the intestines produce the by-product ammonia which is detoxified
by the liver. The liver regulates protein metabolism. The liver also combines
toxic substances including metabolic waste, insecticide residues, drugs,
alcohol, and chemicals with other substances that are less toxic. These
substances are then excreted from the kidneys. Thus, to have proper liver
function, you must have proper kidney function. When either the liver
or the kidney appears to be malfunctioning, treating both organs produces
the best health results.
The primary site of HBV replication is, without surprise, the liver. However, various extrahepatic sites have been proposed. Hemapoetic stem cells have been postulated to support viral replication. This could account for various hematological abnormalities sometimes found in patients with acute hepatitis.
HBV replicative intermediates and/or viral transcripts have also been found in extrahepatic sites. These include mononuclear cells, bile duct epithelial, endothelial, pancreatic acinar cells, and smooth muscle tissue. They have also been found in adrenal glands, gonads, cultured bone marrow, kidneys, lymph nodes, spleen, and thyroid glands of acute hepatitis B infected patients.
