Wound Healing
Physiology of wound healing
Injuries occur every day and normally they heal up quickly. Wound healing is a complex process in which a variety of mediators and reactions ensure its smooth progression. Wound healing can be divided into 5 phases, which to some extent proceed simultaneously:
1. Blood clotting for provisionary wound closure
Blood vessels are the most likely structure to be damaged in case of injury. First objective of the repair process of the body is to stop the bleeding. Platelet aggregation and activation of the coagulation cascade result in blood clotting.
2. Exudation/inflammatory phase
During this phase, the dilation of vessels near the wound leads to a vascular fluid leakage, resulting in an oedema of the wound. This fluid, the so-called exudate, contains a variety of essential substances such as enzymes, antibodies, and growth and inflammation cells, all of them necessary for an undisrupted healing process.
3. Proliferation/ granulation phase
The regeneration of new cells – in order to replace the damaged tissue – predominates during the next wound-healing phase. The new tissue is known as granulation tissue. It fills in the wound from underneath and has a bright red appearance. The build-up of new tissue is performed by fibroblasts (the main cells of the dermis) through synthesis of collagen fibres forming the connective tissue matrix.
4. Epithelization phase
While new vessels are responsible for the transportation of nutrients to the regenerating area, granulation tissue fills the wound and creates the basis for epithelialization: the build-up of a new skin layer. The epithelialization of the wound completes the wound healing process. Epithelial cells divide and migrate from the wound edges and close the wound. Once the covering epithelium beneath a scab is renewed, it peels off and newly built, pink-coloured epithelial tissue underneath becomes visible.
5. Maturation phase
The proper wound healing phase is followed by the maturation phase in which the collagen fibres are reorganized to acquire more strength to the skin. This newly built tissue however is not identical with the original tissue. Scar tissue does not have good blood circulation, is sometimes uneven and less elastic. In addition major variations in colour are possible and in up to 15% of injuries, hypertrophic scar formation can be observed. The process of remodelling of the scar tissue can take years.
Plaster support
In every wound the protective function of the skin is impaired. The objective of wound dressings is to protect the wound and to enable conditions in which healing can proceed as undisturbed as possible, so that the structure can be restored. In the treatment of minor everyday injuries, standard first aid dressings protect the wound from external influences and prevent contamination and infection. They also ensure absorption of blood and secretion, reduce pain and mechanical trauma to a minimum during dressing removal and improve patient’s comfort.