The skin is broadly made up of three parts (from the surface): the epidermis, the dermis, and subcutaneous tissue, each of which plays an important role.
Let's take a look at them from top to bottom.
Skin structure
- Epidermis
- Dermis
- Subcutaneous tissue
The skin is divided into three layers: the epidermis, dermis, and subcutaneous tissue.
Epidermis
The epidermis is about 2 mm thick on average , from the top
④Stratum corneum,
③ Granular layer,
②Stratum spinosum
① The basal layer
It consists of four layers.
■Epidermal turnover
Epidermal cells (epidermal keratinocytes) are produced in the basal layer ①, and when new cells are born, the previous cells are pushed out and move upwards little by little, from the ② spinous layer → the ③ granular layer → to the ④ stratum corneum.
Cells born in the stratum corneum move up to the stratum corneum, and the cells that reach the top (stratum corneum) usually become dandruff and fall off within 28 days. This is called epidermal turnover.
① basal layer → ② spinous layer → ③ granular layer → ④ stratum corneum = 28 days!
■ Structure of the epidermis
①Basal layer:
Longitudinal basal cells are arranged in rows and produce new keratinocytes.
| > Tips) Melanocytes are also found here, and they synthesize the pigment (melanin) that protects the skin from ultraviolet rays. However, if the melanin pigment is not turned over due to aging or other reasons, the pigment remains on the skin and causes spots. |
②Stratum spinosum:
Cells born in the stratum basale become thorny cells in this layer and form a layer (stratum spinosum). This layer receives oxygen and nutrients from the dermis, and proteins that form the stratum corneum and the granular layer that comes next are also synthesized here.
③ Granular layer:
Cells in the spinous layer rise to the top and change shape into flattened cells (granular cells). Two to three layers of these cells overlap to form the granular layer. The proteins that make up the granular cells are broken down into amino acids in the stratum corneum, which then appears, and become the main components of NMF (natural moisturizing factors).
④Stratum corneum:
The cells emerging from the granular cells lose their nuclei and become keratinocytes. 10 to 20 layers of these keratinocytes are piled up to make up the final layer (stratum corneum). This layer contains NMF (natural moisturizing factors) and intercellular lipids , which keep the skin moist and protect it from drying out. On the surface, there is a sebum film made up of a mixture of sebum and sweat, which protects the skin from external stimuli.
-Intercellular lipids
A substance called intercellular lipids fills the spaces between the overlapping layers of stratum corneum cells.
Intercellular lipids have layers of water and oil overlapping to form a lamellar structure, which provides a strong barrier function.
reference)
"Discovery of NMF-producing enzymes and elucidation of a new mechanism for rough skin"
