Most of us take wound healing for granted. If you get a small cut, you may clean and cover it with a bandage, and move on with your life. Yet under that bandage (or in the open air), the body orchestrates a complex cascade of events designed to heal wounds big and small.
Stopping the bleeding (hemostasis). When your skin is cut, scraped, or punctured, you usually begin to bleed. Within minutes or even seconds, unless you have a bleeding disorder, blood cells begin to clump together and clot, protecting the wound and preventing further blood loss. These clots, which turn into scabs as they dry, are created by a type of blood cell called a platelet. The clot also contains a protein called fibrin, which forms a net to hold the clot in place.
Inflammation. Once the wound is closed with a clot, the blood vessels can open a bit to allow fresh nutrients and oxygen into the wound for healing. Blood-borne oxygen is essential for healing. The right balance of oxygen is also important—too much or too little and the wound won't heal correctly. Another type of blood cell, a white blood cell called a macrophage, takes on the role of wound protector. This cell fights infection and oversees the repair process. You might see some clear fluid on or around the cut at this time. That is helping clean out the wound. Macrophages also produce chemical messengers, called growth factors, which help repair the wound.
Growth and rebuilding. Blood cells, including oxygen-rich red blood cells, arrive to help build new tissue. Chemical signals instruct cells to create collagen, which serves as a type of scaffolding, and other tissues to begin the repair process. Occasionally, you see the result of this process as a scar that starts out red and eventually dulls. Within a week, the repair is 10 percent as strong as the original.
Strengthening. Over time, the new tissue gets stronger. You might notice stretching, itching, and even puckering of the wound as that happens. Within three months, the wound is about 70 percent as strong in its repair as it was before the trauma. The entire healing process might take a couple of years to complete.
The process seems simple enough, but wound healing is actually quite complicated and involves a long series of chemical signals. Certain factors can slow or prevent healing entirely.
One of the most dramatic factors is reduced or inadequate blood supply to the wound. The oxygen and nutrients that new blood carries to the wound are essential to successful healing. A wound that is not getting enough blood could take at least twice as long to heal, if it heals at all. By some estimates, as many as 6.5 million people in the United States suffer with wounds that are not healing well. These are called chronic wounds, which are more common in people with diabetes, high blood pressure, obesity, or other vascular disease.
If you have a wound that is not healing in a reasonable time frame, make an appointment with your health care provider. If your injury seems to be getting worse or appears infected—that is, if it is more swollen, hot to the touch, painful, or oozing pus—see a doctor immediately.