Healing refers to the restoration of damaged or diseases part of the body. Wound healing is an intricate process of repair after injury. Skin is a protective barrier against the external harms. When this barrier is broken down, healing process sets in. Wound healing process includes three phases: inflammation, proliferation and remodeling.
Inflammatory phase: It is a protective phenomenon after tissue injury as it eliminates the injury initiating factors and restores the function. Just before the inflammatory phase commences, tissue hemostasis sets in and stops the bleeding. Soon after the hemostasis process, certain chemicals such as cytokines and chemokines are released to attract and stimulate immunity cells to kill or eat the harming bacteria or debris. Clotting cascade activates and aggregates platelets and forms plug with the help of certain proteins called fibrin and fibronectin. Growth factors are released from platelets which speed up the wound repair by increasing the cell divisions. Processes of vasoconstriction and vasodilatation further maintain the homeostasis. Neutrophils and macrophages secrete proteases and kill and phagocytize bacteria, damaged tissue and debris.
Proliferative phase: As soon as the inflammatory phase dies down, proliferative phase commences. In this phase fibroblasts and endothelial cells migrate to the injured site and pave way for angiogenesis, fibroplasia and granulation tissue formation. Fibroblasts produce collagen protein which is most important in order to strengthen the healing wound. Granulation tissue helps re-epithelialization of the wound site, reestablishing the protective barrier.
Remodeling: Collagen is the main healing protein. When collagen deposition and degradation equalizes, remodeling process begins. Collagen type III of proliferative phase is replaced by stronger collagen type I during remodeling. In this process, collagen fibers are rearranged, cross-linked and aligned to offer maximum tensile strength to the wound. Collagen deposition to the wound site causes scar formation. All the wounds end up with scars except for minor cuts and abrasions. Current medical science aims at wound healing with minimal scarring and more perfect tissue reconstruction.