Wound healing is a complex and dynamic process of replacing devitalized and missing cellular structures and tissue layers. The human adult wound healing process can be divided into 4 distinct phases- hemostasis phase, the inflammatory phase, the proliferation phase, and the remodeling phase.
1.Hemostasis: Within the first few minutes of injury, platelets in the blood begin to stick to 　the injured site.
2.Inflammation: During this phase, damaged and dead cells are cleared out, along with 　bacteria and other pathogens or debris.
3.Proliferation: In this phase, angiogenesis, collagen deposition, granulation tissue formation, 　epithelialization, and wound contraction occur.
4.Remodeling: During maturation and remodeling, collagen is realigned along tension lines, 　and cells that are no longer needed are removed by programmed cell death.
　　The wound healing process is not only complex but also fragile, and it is susceptible to interruption or failure leading to the formation of non-healing chronic wounds. Factors that contribute to non-healing chronic wounds are diabetes, venous or arterial disease, infection, and metabolic deficiencies of old age.