Which of the following is "a linear crack extending from the epidermis to the dermis"?

A fissure is defined as a linear crack that extends from the outermost layer of skin, the epidermis, down into the deeper layer, the dermis. This type of skin lesion often appears in areas where the skin is subjected to stress or prolonged dryness, leading to cracks that can be painful and sometimes become infected. Fissures can occur in various locations on the body and are typically narrow with defined edges.

Ulcers, on the other hand, are deeper skin losses that extend through the epidermis and dermis and may involve subcutaneous tissue; they usually have a larger surface area compared to fissures. Lichenification refers to the thickening of the skin that occurs from chronic scratching or irritation, leading to a leathery texture, but it is not a crack. An excoriation is a scratch or abrasion on the skin, often superficial, which does not extend as deeply as a fissure. Thus, a fissure is distinctly recognized by its linear depth and the specific layers of the skin it affects.