Epithelialization is a fundamental biological process involved in the natural healing of wounds. It represents a precise and coordinated effort by the body to repair damaged skin or other epithelial surfaces. During this phase, specialized skin cells, known as epithelial cells, actively multiply and spread across the wound bed. This cellular activity is important for closing the wound, re-establishing the skin’s protective barrier, and protecting underlying tissues.
Visual Characteristics
Epithelialization presents distinct visual characteristics. The newly formed epithelial layer often appears as a pale pink or light red, sometimes even a slightly translucent color. This new tissue can also have a shiny or pearly white appearance, distinctly lighter than the deeper red of underlying granulation tissue. Its texture is typically smooth, flat, and delicate, lacking the bumpy or granular surface of granulation tissue. A moist appearance can accompany this new, thin layer of skin.
This delicate new skin usually begins to form from the edges of the wound. For some wounds, especially those that are deeper or larger, epithelialization can also originate from residual skin structures within the wound bed, such as hair follicles or sweat glands. The emerging tissue is a thin, fragile layer, often only a few cell layers in thickness, and quite vulnerable to damage.
How It Progresses
The visual progression of epithelialization unfolds as a dynamic process of wound closure. Initially, a thin, slightly raised, pink or white rim of new tissue becomes noticeable along the wound margins. This signifies epithelial cell migration from the wound edges. These cells then begin to advance inward, gradually reducing the overall size of the open wound.
As the process continues, the new tissue extends across the wound surface. For larger or more complex wounds, small, isolated “islands” of new skin may also emerge within the wound bed. These islands originate from surviving epithelial cells in hair follicles or sweat glands. These individual islands then expand, eventually merging with each other and with the epithelial tissue advancing from the wound edges, until the entire wound surface is covered. Once the migrating epithelial cells meet and cover the wound, contact inhibition halts further migration, signaling resurfacing completion.
Differentiating from Other Wound Appearances
Epithelialization must be distinguished from other tissue types commonly found in a healing wound. Granulation tissue, which provides the foundation for epithelialization, appears as a deep red, beefy, and bumpy tissue. In contrast, epithelialization is paler, smooth, and flat, forming a superficial layer over the granulation tissue rather than being part of it. Granulation tissue does not transform into epithelium; it is covered by it.
It is also important to differentiate epithelialization from non-viable tissues like eschar and slough. Eschar is dark, often black, leathery, and dry dead tissue. Slough, conversely, is yellow or white, stringy or adherent, and consists of dead tissue that can impede healing. Unlike these non-living materials, epithelialization is a clean, orderly process of living, growing tissue. Signs of infection, such as thick, colored pus, excessive redness, swelling, increased pain, or foul odor, are distinct from healthy epithelialization; epithelializing wounds are clean, without these indicators of bacterial presence.