t4
The epidermis is the superficial, avascular layer of skin. It is the epidermis that the physician desires to
manipulate during dermabrasion. Knowledge of its substructure is important in understanding skin regeneration
following dermabrasion, or for that matter following a thermal or chemical burn.
The cells of the epidermis are arranged in strata (layers). The stratum basalis consists of cuboidal cells
adherent to the basement membrane; these cells divide mitotically to give rise to all cell layers of the epidermis.
The cell layerjust above the S. basalis takes on spiny edges because of cell-to-cell adhesions, and this layer is
known as the stratum spinosum. As granules of keratin are synthesized, [vrny purple staining ribosomes give
the epidermal cells a granular appearance, so the next cell layer is termed the stratum granulosum. As the
ribosomes are no longer needed, they disappear. The nuclei condense and also become nonvisible. The cells
take on a clear, or lucid, appearance, so the next cell layer is termed the strafum lucidum. The stratum corneum
is the outermost layer, consisting of dead cells that eventually desquamate.
If the stratum basalis, which gives rise to all epidermal cell layers were destroyed, skin regeneration would be
very difficult, but not impossible. Close examination of skin histology will show that the stratum basalis extends
into the dermis as part of the hair follicles and glands of the dermis, changing name according to the structure
involved. If the stratum basalis is destroyed, such as during excessive dermabrasion or from a severe skin burn,
hair follicles and dermal glands will contribute to epidermal regeneration.
The goal of dermabrasion is to remove all layers of the epidermis except for the stratum basalis. Realistically
this is not entirely possible, because of the limitations of human skill during the procedure. Some areas of the
skin will not have adequate layers of cells removed. Some areas of the skin will have skin removal down to and
into the dermis; this explains the bleeding and pain associated with dermabrasion. A good dermatologist will,
however, perform the procedure so that most areas of the skin will have cells removed down to, but not
including, the stratum basalis.
Questions
1.
What layer (stratum) of the skin epidermis divides mitotically to form the epidermis cell layers?
2.
What structures in the dermis can also regenerate skin (to a limited degree)? Why?
3.
What layers of the epidermis could the dermatologist safely remove and still allow for epidermis
regeneration?
the entire epidermis and most of the dermis. Would a skin graft be needed
for a third degree burn? How could you determine if it were a third degree burn, as opposed to a less
severe burn?
4. A third degree burn involves