Wounds that are stitched closed are said to heal by “first intention.” The edges of the wound are brought and held together with sutures and will immediately begin to link together with new cells to repair the area. You won’t be able to see the work the body is doing below the surface of the sutured skin, but rest assured it’s happening.
For those wounds that cannot be sutured and are left to open, the process is called “second intention healing.” You’ll be able to observe the three phases of this type of healing with each bandage change:
1. Granulation. During this phase, the body fills any tissue defect below the level of the skin surface with granulation tissue, which is primarily a mix of blood vessels and collagen. Bumpy and red or reddish yellow, granulation tissue fills the depths of the wound first then works its way to the surface. Granulation tissue in a wound is a sign that healing is occurring.
2. Epithelization. This phase of wound healing begins after granulation tissue has filled the entire wound defect. At that point, new skin cells—called epithelial cells—begin to form at the edges of the wound and spreading across the new bed of granulation tissue to meet each other in the center. You’ll recognize epithelial cells as the pinkish looking rim around the granulation tissue of healing wound. Epithelial cells can only move laterally, not up or down, which is a consequential limitation; The wound-healing complication known as proud flesh occurs when granulation tissue rises above the edge of the wound, preventing epithelial cells from covering it.
3. Contraction. This phase overlaps with epithelization and is what ultimately reduces the size of the wound. Muscle fibers within granulation tissue contract as the defect is full, pulling the edges of the wound together. When healing is uninterrupted, this happens quickly, with some equine wounds, literally, shrinking overnight.