This is an intricate process in which the skin (or other organ) repairs itself after injury.
In normal skin, the epidermis and the dermis exists in steady-state equilibrium, forming a protective barrier against external environment. If this barrier is broken, the normal process of wound healing is immediately set in motion which is divided into three to four sequential, yet overlapping phases.
Phase One: Inflammatory, Phase Two: Proliferative and Phase Three: Remodeling Phase.
Upon injury a set of complex biochemical events takes place to repair the damage. In minutes post-injury, platelets aggregate at the injury site to form a fibrin clot which acts to control active bleeding.
Phase Four: Inflammatory Phase.
This is where bacteria and debris are phagocytosed and removed. Factors are released that cause the migration and division of cells involved in the Proliferative Phase. This phase is characterized by angiogenesis, collagen deposition, granulation tissue formation, epithelialization and wound contraction. In angiogenesis, new blood vessels are formed by vascular endothelial cells.
In fibroplasias and granulation tissue formation, fibroblasts grow and form a new, provisional extracellular matrix by excreting collagen and fibronectin. Concurrently, re-epithelialization of the epidermis occurs, in which epithelial cells prolifearate and crawl to the top of the wound bed providing cover for the new tissue.