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The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. [1] The epidermal layer provides a barrier to infection from environmental pathogens [2] and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. [3]
Others serve to anchor the epidermis glabrous skin (hairless), and hyper-proliferative epidermis (from a skin disease). [1] They divide to form the keratinocytes of the stratum spinosum, which migrate superficially. [2] Other types of cells found within the stratum basale are melanocytes (pigment-producing cells) and Merkel cells (touch receptors).
In the deeper layers, the cells may be columnar or cuboidal. [1] There are no intercellular spaces. This type of epithelium is well suited to areas in the body subject to constant abrasion, as the thickest layers can be sequentially sloughed off and replaced before the basement membrane is exposed.
A diagram displaying the layers of the epidermis, with basal cells comprising the stratum basale. In the epidermis, basal cells function as unipotent stem cells. [5] Found in the lowest layer of the epidermis, the stratum basale, basal cells continuously divide in order to replenish the squamous cells that make up the skin's surface. [6]
Micrograph of keratinocytes, basal cells and melanocytes in the epidermis Keratinocytes (stained green) in the skin of a mouse. Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells. [1]
The main type of cells that make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, and basale. Cells are ...
The epidermis is regenerated from the stem cells found in the basal layer that develop into the corneum. The epidermis itself is devoid of blood supply and draws its nutrition from its underlying dermis. [5] Its main functions are protection, absorption of nutrients, and homeostasis.
Histologic image of the epidermis with its layers named in white text.. The Malpighian layer (stratum mucosum or stratum malpighii) of the epidermis is generally defined as both the stratum basale (basal layer) and the thicker stratum spinosum (spinous layer/prickle cell layer) immediately above it as a single unit, [1] [2] although it is occasionally defined as the stratum basale specifically ...