Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of permanent scar tissue.Repeated injuries, chronic inflammation and repair are susceptible to fibrosis where an accidental excessive accumulation of extracellular matrix components, such as the collagen is produced by fibroblasts, leading to the formation of a permanent fibrotic scar.In response to injury, this is called scarring, and if fibrosis arises from a single cell line, this is called a fibroma. Physiologically, fibrosis acts to deposit connective tissue, which can interfere with or totally inhibit the normal architecture and function of the underlying organ or tissue. Fibrosis can be used to describe the pathological state of excess deposition of fibrous tissue, as well as the process of connective tissue deposition in healing. Defined by the pathological accumulation of extracellular matrix (ECM) proteins, fibrosis results in scarring and thickening of the affected tissue — it is in essence an exaggerated wound healing response which interferes with normal organ function. Physiology
Fibrosis is similar to the process of scarring, in that both involve stimulated fibroblasts laying down connective tissue, including collagen and glycosaminoglycans. The process is initiated when immune cells such as macrophages release soluble factors that stimulate fibroblasts. The most well characterized pro-fibrotic mediator is TGF beta, which is released by macrophages as well as any damaged tissue between surfaces called interstitium.
Brain
Glial scar

Heart
Myocardial fibrosis has mainly two forms:

Interstitial fibrosis, which has been described in congestive heart failure, hypertension, and normal aging. Replacement fibrosis, which indicates an older myocardial infarction. Other
Arterial stiffness
Arthrofibrosis (knee, shoulder, other joints)
Chronic kidney disease
Crohns disease (intestine)
Dupuytrens contracture (hands, fingers)
Keloid (skin)
Mediastinal fibrosis (soft tissue of the mediastinum)
Myelofibrosis (bone marrow)
Peyronies disease (penis)
Nephrogenic systemic fibrosis (skin)
Progressive massive fibrosis (lungs); a complication of coal workers pneumoconiosis
Retroperitoneal fibrosis (soft tissue of the retroperitoneum)
Scleroderma/systemic sclerosis (skin, lungs)
Some forms of adhesive capsulitis (shoulder)

References
External links
 Media related to Fibrosis at Wikimedia Commons