Protection from mechanical injury, chemical hazards, and bacterial invasion are provided by the skin because the epidermis is relatively thick and covered with keratin. The secretions of the sebaceous glands and sweat glands are also beneficial for this protective shield. If injuries damage the skin, the body triggers a response called wound healing. After hemostasis, inflammation of white blood cells, including phagocytic macrophages arrive at the site of injury. Once the attacking microorganisms have been controlled, the skin will heal itself. The ability of the skin to heal even after considerable damage occurs due to stem cells in the dermis and cells in the epidermal stratum basal, all of which can produce new tissue.
As the injury extends through the epidermis to the dermis, bleeding occurs and the inflammatory response begins. The blood clotting mechanism is immediately activated, and a blob of scab is formed within a few hours. Scabs temporarily restore epidermal integrity and limit the entry of microorganisms. Once the scabies are formed, the stratum basale cells begin to divide by mitosis and migrate to the edge of the scab. A week after the injury, the wound edges are pulled together by contractions. Contractions are an important part of the healing process when the damage has been widespread, and involves the shrinking of the size of the underlying contractile contractile connective tissue, which brings the wound margin toward each other. In major injuries, if epithelial cell migration and tissue contractions can not cover the wound, sewing the edges of the wounded skin together, or even replacing the lost skin with a skin graft, may be necessary to restore the skin.
As epithelial cells continue to migrate around the scab, the dermis is corrected by the activity of the stem cells. These active cells produce collagen fibers and basic substances. The blood vessels soon grow into the dermis, restoring circulation. If the injury is very small, the epithelial cells eventually restore the epidermis after the dermis has been regenerated.
In major injuries, repair mechanisms can not restore the skin to its original state. The repaired region contains a large number of abnormal collagen fibers, and relatively few blood vessels. Persistent sweat and sebaceous glands, hair follicles, muscle cells, and nerves are rarely repaired. They are usually replaced by fibrous tissue. The result is the formation of scar tissue that is not flexible and fibrous.
Video Skin repair
See also
- Wound healing
Maps Skin repair
References
Source of the article : Wikipedia
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