Why do small burn injuries leave a more permanent scar on the skin than scrapes or scratches?

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Why do small burn injuries leave a more permanent scar on the skin than scrapes or scratches?

In: Biology

Scrapes and scratches can leave scars too. Anyone who has ever had a kitten will know how real the struggle is.

Burns simply do a lot more damage, usually over a wider area, meaning the scarring is worse. Boiling water for example, continues doing damage to the affected tissue for a considerable period of time if the affected area is not cooled down quickly and in the correct way, causing even more damage.

The answer likely pertains to the layers of tissue that are damaged by a burn.

The epidermis (the outer layer of the skin) consists of several layers of cells that constantly slough off and are replaced by [basal cells (in the stratum basale in this image)](https://usercontent2.hubstatic.com/13001389_f520.jpg), which are specialized stem cells that live at the border between the epidermis and the deeper layers of the skin.

When you sustain a superficial (shallow) cut or scratch, it’s hard to take out too many basal cells at once (unless the wound is very deep or wide). Thus, the basal cells are usually spared and will eventually be activated to produce new skin cells (called keratocytes), regenerating the epidermis. This allows effective healing without scar formation.

However, even a relatively small thermal burn can cause heat energy to easily penetrate to deeper layers of the skin over a larger area, potentially obliterating or deactivating the basal cells that would otherwise allow for regeneration. In the absence of functional basal cells, other healing mechanisms are activated (such as the invasion of fibroblasts, which produce collagen and other elements that form scar tissue) that leave behind a persistent scar.