Scars Burn Graze
If your skin is damaged in any way, such as a cut, a graze, a burn, a spot or a surgical scar, a remarkable sequence of events takes place to heal it. A paper cut, for example, is usually gone the next day, while a playground graze heals secretly beneath a scab. Sometimes a cut heals more slowly than at other times, though it's noticeable how quickly most children are left with barely a scar after a nasty graze on the knee. For this regeneration to take place well and quickly, we need a range of nutrients.
When the skin has been injured, cells in the epidermis break away from the base, enlarge and move across the opening until it is entirely covered. There appears to be a mechanism which makes them stop moving when they encounter a similar cell, so this migration automatically stops once the surface of the wound is well covered. While this is happening other cells divide and replace those that have migrated across the open space. Then the cells that have formed the new skin themselves multiply to thicken the new surface.
However, if a wound goes deeper into the skin, the process is more complicated. The first step involves inflammation. The purpose of this is to increase the blood supply to the damaged area so that any microbes, or other foreign bodies that may have got into the skin, as well as dead cells, can be taken away. During this stage blood clots are also created around the broken skin to loosely seal the edges. In addition the swelling and inflammation provide a speedier delivery of immune cells which round up any microbes and other cells to help the clotting process. The clot then forms a scab to cover the wound, while the cells beneath can travel across the gap to continue the healing.
In the next stage the cells multiply dramatically so that the damaged blood vessels grow back and collagen fibres form. Once the epidermis underneath the scab is back to its normal thickness, the scab can fall off: A scar may remain where the wound was - if it goes beyond the original skin damage it is what is known as a keloid scar. The difference between normal tissue and scar tissue is that scar tissue is more densely packed with collagen.