Phases of wound healing

Hemostasis

-1st phase -occurs immediately after the initial injury -involved blood vessels constrict and blood clotting begins thru platelet activation and clustering. -after only a brief period of constriction, these same blood vessels dilate and capillary permeability increases, allowing plasma and blood components to leak out into the area that is injured, forming a liquid called exudate

Inflammatory phase

-2nd phase -follows hemostasis and lasts about 4-6 days. -white blood cells, predominantly leukocytes and macrophages, move to the wound. Leukocytes arrive first to ingest bacteria and cellular debris. About 24 hrs after the injury, macrophages (a larger phagocytic cell) enter the wound area and remain for an extended period. -during this phase, the pt has a generalized body response, including a mildly elevated tempt, leukocytosis (increased number of white blood ells in the blood), and generalized malaise.

Proliferation phase

-3rd phase -lasts for several weeks. -new tissue is built to fill the wound space, primarily thru the action of fibroblasts. Fibroblasts form fibrin that stretches through the clot. A thin layer of epithelial cells forms across the wound, and blood flow across the wound is reinstituted. -the new tissue called granulation tissue forms the foundation for scar tissue development. It is highly vascular, red, and bleeds easily. In wounds that heal by first intention, epidermal cells seal the wound within 24 to 48 hrs, thus granulation tissue is not visible. -collagen synthesis

maturation phase

-4th and final phase -beings about 3 weeks after the injury, possibly continuing from months or years. -new collagen continues to be deposited, which compresses the blood vessels in the healing wound, so that the scar, an avascular collagen tissue, eventually becomes a flat, thin line.