Scars are areas of fibrous tissue that replace normal skin (or other tissue) after injury. A scar results from the biologic process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound (e.g. after accident, disease, or surgery) results in some degree of scarring.
Scar tissue is not identical to the tissue which it replaces and is usually of inferior functional quality. For example, scars in the skin are less resistant to ultraviolet radiation, and sweat glands and hair follicles do not grow back within scar tissue. A myocardial infarction, commonly known as a heart attack, causes scar formation in the heart muscle which leads to loss of muscular power and possibly heart failure. However, there are some tissues (e.g. bone) which can heal without any structural or functional deterioration, and in fact bone tissue may be structurally stronger after a break.
The word scar was derived from the Greek word eschara, meaning place of fire (fireplace).
How scarring occurs
A scar is a natural part of the healing process. Skin scars occur when the deep, thick layer of skin (the dermis) is damaged. The worse the damage is, the worse the scar will be.
Most skin scars are flat, pale and leave a trace of the original injury which caused them. The redness that often follows an injury to the skin is not a scar, and is generally not permanent. The time it takes for it to go away may, however, range from a few days to, in some serious and rare cases, several years. Various treatments can speed up the process in serious cases.
Scars form differently based on the location of the injury on the body and the age of the person who was injured.
This process results in a fortuna scar. Because the body cannot re-build the tissue exactly as it was, the new scar tissue will have a different texture and quality than the surrounding normal tissue. An injury does not become a scar until the wound has completely healed.
Transforming Growth Factors (TGF) play a critical role in scar development and current research is investigating the manipulation of these TGFs for drug development to prevent scarring from the emergency (and rather inappropriate) adult wound healing process.
Two types of scars are the result of the body overproducing collagen, which causes the scar to be raised above the surrounding skin. Hypertrophic scars take the form of a red raised lump on the skin, but do not grow beyond the boundaries of the original wound, and they often improve in appearance after a few years. Keloid scars are a more serious form of scarring, because they can carry on growing indefinitely into a large, tumorous (although benign) growth.
Both hypertrophic and keloid scars are more common on younger and darker-skinned people. They can occur on anyone, but some people have a genetic susceptibility to these types of scarring. They can be caused by surgery, an accident, or sometimes by acne. In some people, keloid scars form spontaneously.
Although they can be a cosmetic problem, keloid scars are only inert masses of collagen and therefore completely harmless, painless, and non-contagious. They tend to be most common on the shoulders and chest. Keloid scars are most common among people of Asian or African descent.
Alternately, a scar can take the form of a sunken recess in the skin, which has a pitted appearance. These are caused when underlying structures supporting the skin, such as fat or muscle, are lost. This type of scarring is commonly associated with acne, but can be caused by chickenpox, surgery or an accident.
Scars can also take the form of stretched skin. These are caused when the skin is stretched rapidly (for instance during pregnancy, significant weight gain or adolescent growth spurts), or when skin is put under tension during the healing process, (usually near joints). This type of scar usually improves in appearance after a few years.