Definition: Think of fibrosis as a scar. When the skin gets injured, sometimes a scar will form during the healing process. The scar is made from specialized tissue (called "connective tissue"), which is what "fills in" the damage. Much the same way that a scar forms on the skin, scars can form in other parts of the body too. Extensive scarring of the liver and other internal organs of the body is termed "fibrosis."
Liver fibrosis begins at the cellular level. Liver cells (called "hepatocytes") can be injured by many things. One common way is by viruses, including the five viruses that specifically cause hepatitis. Whenever hepatocytes are infected with a virus, the body's immune system is stimulated, resulting in inflammation. If the immune system isn't able to get rid of the virus soon enough, chronic inflammation will lead to fibrosis. Extensive fibrosis leads to cirrhosis.
