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When we are small, we usually have to endure many different types of injuries such as burns, cuts, and knocks or bangs in our body. These injuries become less during adulthood, but we still sustain them well. How is it possible? Well, all of these aggressions commence an orderly set of events that are involved in the healing response, in which the normal healthy tissue (skin) is replaced by connective tissue (scar). The healing response is also characterized by the movement of specialized cells into the injury site.

The restoration of anatomical continuity and function is the result of the complex and dynamic process of healing. There are four basic responses that can happen after an injury:

1.Regeneration (exact replacement)

Regeneration occurs when there is loss of structure and functionality. The beauty of our organism is that it has the complex capacity to restore that tissue by replacing exactly what was there before the injury. Smaller forms of life, such as the salamander and crab, can regenerate tissue in this way. As man has evolved, we have lost this capacity and can only recuperate a limited amount of damaged tissues by the process of regeneration.

2. Normal repair (reestablished equilibrium)

Normal repair is the instance where there is a re-established equilibrium between scar creation and scar remodeling. This is the usual response that most humans develop after an injury. The pathological response to tissue injury stand in sharp contrast to the healthy repair response.

3. Excessive healing (fibrosis and contractures)

In excessive healing there is an exaggerated deposition of connective tissue; this produces an altered tissue and, thus, loss of functionality. Fibrosis, structures, adhesions and contractures are consequences of exaggerated healing. Keloids and hypertrophic scars in the skin are examples of fibrosis. Contraction is normal during the process of healing but if exaggerated, it becomes pathologic and is called a contracture.

4. Deficient healing (chronic ulcers)

Deficient healing is the opposite of fibrosis; it appears when there is an abnormally low deposition of connective tissue matrix and the tissue is thinned to the point where it can fall apart. Chronic non-healing ulcers are examples of deficient healing.

The Skin's Natural Healing Process

Just as an injury occurs, several different cells are sent to the damaged site, and the complex healing process begins.

The normal healing cascade starts with an orderly process of hemostasis and fibrin deposition, which initiates an inflammatory cell cascade, characterized by neutrophils, macrophages and lymphocytes within the tissue. This is followed by attraction and synthesis of fibroblasts and collagen deposition, and finally remodeling by collagen cross-linking and scar maturation. Despite this orderly sequence of events leading to normal wound repairing, pathologic reactions leading to fibrosis or chronic ulcers may occur if any part of the healing sequence is altered.