Wound Healing

Wound healing is an intricate play involving a number of main features and supporting systems. Understanding wound healing is essential to understanding skin regeneration and disease healing.

The process of wound healing occurs in three main phases: inflammation, proliferation and tissue formation and remodeling. Each phase is marked by a series of complex interactions between many cell types, blood elements, growth factors and extracellular matrix. These phases do not represent separate or distinct events, they overlap and are continuous.

The Three Phases of Wound Healing

Phase 1
Inflammation
Platelets
Blood coagulation
Leukocytes

Phase 2
Proliferation and tissue formation
Keratinocyte migration and integrans
Fibroplasia
Angiogenesis

Phase 3
Tissue remodeling
Fibronectin
Proteoglycans
Collagen

The initiation is through inflammation. At the onset of inflammation it is platelets are released from the blood by local blood vessel damage. Triggered by thrombin and fibrillar collagen, the platelets release a number of mediators. In the presence of the released responses from surrounding cells the platelets begin aggregating and more platelets are brought by chemical mediators to the site. The result is a plug, the first stage of stopping the wound. The leakage of plasma and other elements from injured blood vessels begin thrombus formation by both of the major clotting pathways, the intrinsic and extrinsic. The whole forms a complex cross linkage of protein-glycans mesh rich in immune cells and proliferation factors.

In the proliferation phase keratinocytes take over from platelets. This is a gradual process. Keratinocytes undergo a change in morphology and migrate to cover the wound. In the skin the reconstitution of the damaged epidermis and basal membrane begins as granulation tissue and scab. In later stages the intricate reconstruction of dermis, vessels, nerves and other tissue continues along side fibrotic scar formation where the reconstruction is too massive to be accomplished by the system.