What Is a Skin Incision?

Skin wound healing refers to the healing process after the skin tissue is cut off or damaged due to external force. It includes the complex combination of regeneration of various tissues, hyperplasia of granulation tissue, and formation of scar tissue, showing synergistic effects of various processes.

Skin wound healing

Skin wound healing refers to the healing process after the skin tissue is cut off or damaged due to external forces, including the regeneration and repair of various tissues.

The former can be healed by epithelial regeneration, and the latter two have serious trauma, and the skin itself cannot be repaired and healing often requires manual intervention, such as skin repair surgery and skin grafting. If the skin appendages (hair follicles, sweat glands, and sebaceous glands) are completely damaged, they cannot be completely regenerated, and scar repair occurs. After the tendon is ruptured, the scar is also repaired in the initial stage. However, as the function is continuously rebuilt, collagen fibers can be aligned in the direction of the original tendon fibers to achieve complete regeneration.

1. Early changes in the wound There are different degrees of tissue necrosis and vascular rupture and bleeding in the wound. The inflammatory reaction occurs within a few hours, which is manifested as congestion, serous exudation, and leukocyte migration, so local swelling. Early neutrophil infiltration was predominantly neutrophils, and after 3 days they were mainly macrophages. The fibrinogen in the blood and exudate in the wound quickly coagulates to form a clot, and some of the clot surface is dried to form crusts. Clots and crusts protect the wound. 2. After 2 to 3 days of wound contraction, the entire layer of skin and subcutaneous tissue at the edge moves to the center, so the wound shrinks rapidly and stops around 14 days. The significance of wound contraction is to reduce the wound surface. However, in various specific cases, the degree of wound shrinkage varies depending on the wound site, wound size and shape. Wound contraction is caused by the pulling effect of new myofibroblasts at the edge of the wound, and has nothing to do with collagen. Because the contraction of the wound happens to be the time of myofibroblast proliferation.

3. Granulation tissue formation and scar formation From the third day, granulation tissue grows from the bottom and edges of the wound to fill the wound. Capillary blood vessels grow at a rate of about 0.1-0.6 mm per day. Most of its directions are perpendicular to the wound surface, and are curved in a shape. There are no nerves in the granulation tissue, so there is no sensation. Fibroblasts produced collagen fibers from the 5th to 6th day. The collagen fiber formation was very active one week later, and then gradually slowed down. With more and more collagen fibers, a scar formation process occurs, and the scar is completely formed about one month after the injury. It is possible that due to local tension, the collagen fibers in the scar eventually parallel the skin surface.

4. Within 24 hours after the epidermis and other tissue regeneration wounds occur, the basal cells at the edge of the wound begin to proliferate and migrate under the clot to the wound center to form a single layer of epithelium that covers the surface of the granulation tissue. When these cells meet each other, they stop migrating and proliferate and differentiate into squamous epithelium. Healthy granulation tissue is important for epidermal regeneration because it provides the nutrients and growth factors needed for epithelial regeneration. If the granulation tissue cannot fill the wound and form scars for a long time, the epithelial regeneration will be delayed; in another case, the exuberant granulation, which is overgrown due to the stimulation of foreign bodies and infections, is high on the skin surface, It also prevents epidermal regeneration, so it is often necessary to remove it clinically. If the wound is too large (generally considered to be more than 20cm in diameter), it is difficult for the regenerated epidermis to completely cover the wound, and skin grafting is often required.