Epidermal Wound Healing

The exposed location of the skin (and mucous membranes) makes it vulnerable to trauma as a result of physical and chemical stimuli (stresses).

One common type of epidermal wound is an abrasion (scraped away area) such as might be experienced in the form of a skinned knee or elbow. Another type is a first-degree or second-degree burn. 

In an epidermal wound, the central portion of the wound may extend to the dermis, while the edges of the wound usually involve only slight damage to superficial epidermal cells.

In response to injury, basal epidermal cells in the area of the wound brea their contacts with the basement membrane. These cells then enlarge and migrate across the wound. The cells appear to migrate as a sheet until advancing cells from opposite sides of the wound meet. When epidermal cells encounter each other, their continued migration is stopped by contact inhibition. 

According to this phenomenon, when one epidermal cell encounters another, its direction of movement changes until it encounters another like cell, and so on. 

Continued migration of the epidermal cell stops when it is finally in contact on all sides with other epidermal cells. Contact inhibition appears to occur only among like cells; in other words contact inhibition does not occur between epidermal cells and other types of cells. 

Malignant cells do not conform to the rules of contact inhibition and so they have the ability to invade body tissues with few restrictions. 

Simultaneous with the migration of some basal epidermal cells, stationery basal stem cells divide to replace the migrated ones. Migration continues until the wound is resurfaced. Following this, the migrated cells themselves divide to form new strata, thus thickening the new epidermis. The events involved in epidermal wound healing occur within 24 to 48 hours after wounding.