Epidermis is the most external layer of the skin. It consists mostly of a row or groups of epithelial cells (stratified epithelium) and other types of cells that provide immune protection. The epidermis is avascular (does not contain blood vessels), so it doesn’t receive nutrients. Only the deepest layer of the epidermis is nourished, named basal membrane, which is in contact with the dermis and firmly attached to it.
The different cell blocks that we find in the epidermis are:
- Keratinocytes: they make a protein called keratin, and form the protective cover of the epidermis, creating between 25-30 layers of cells that migrate from the deepest layer to the most external. The most superficial layer is detached as new cells arrive in a continuous and rapid process, speed of detachment depending on cell age and external and internal factors. Epidermis is impermeable and protects skin and tissues from external aggressions.
- Melanocytes: located in the deepest layer of epidermis, called melanocytes because they synthesize a pigment called melanin, which is responsible for skin pigmentation when exposed to sunlight. This pigmentation is a protection system, and although it’s produced by melanocytes, it’s transferred to keratinocytes spreading the characteristic tan color and extending the protection. The different human races have practically the same number of melanocytes, but people with dark skin tones have a higher activity in this cell type. Their functionality can be altered by external and internal factors, causing inestetisms such as hyperpigmentation, lentigines, melasmas, etc…
- Langerhans’ cells: this group of cells come from the bone marrow and migrate to the epidermis. Their function is phagocytic (they consume or destroy harmful organisms), and they are also antigen presenters to lymphocytes, causing contact hypersensitivity reactions (dermatitis or allergic reactions). They are generally located in the spiny, granular and basal layers of epidermis, which we will detail later.
- Merkel cells: located in the basal layer of epidermis and their functions are related to mecanosensation (sense of touch) and neuroendocrine secretion.
Epidermis layers are divided into four strata: basal or germinative stratum, spinosum stratum, granulosum stratum and corneum stratum.
Basal or germinative stratum is the deepest, consists of a single layer of keratinocytes with a great capacity for division. This layer is firmly seated on a membrane that forms the dermo-epidermal junction, links epidermis and dermis. The keratinocytes found in this layer are the only ones that have the capacity to proliferate and are interspersed with melanocytes in a proportion of one for every ten.
The spinosum or squamous stratum is made up of approximately ten rows of epithelial cells, which flatten out as they migrate to the surface.
The granular stratum is made up of two or three rows of very flattened cells that have cytoplasmic granules for the keratinization process. In thick skin areas, such as palms and soles, this stratum has a subdivision called lucid stratum, but it’s only a transitional division without much histological significance.
The stratum corneum is composed of up to thirty rows of “cornified” cells. These structures have no nucleus and are only keratin fibers that continuously shed.
Saurina Institut Científic always recommend weekly exfoliations to help our skin in its natural regeneration process, to keep the stratum corneum as homogeneous as possible. With this we manage to minimize problems of hyperpigmentation, small marks and wrinkles are minimized, dehydration is improved, skin is more oxygenated and prepared to receive benefits of usual cosmetic treatment.
Our recommendation to take care of yourself at home is to use products with nanotechnological base, such as Nano by Saurina (www.nanobysaurina.eu).
Nano by Saurina helps us recover keratinocytes and melanocytes regeneration, avoids and treats alterations described above, and manages to act on the dermis (the intermediate layer of the skin where cellular processes, essential for maintaining healthy skin, are carried out).