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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 .
The epidermis of most leaves shows dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions. Woody stems and some other stem structures such as potato tubers produce a secondary covering called the periderm that replaces the epidermis as the protective covering.
The epidermis, "epi" coming from the Greek language meaning "over" or "upon", is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface, which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina.
The stratum corneum (Latin for 'horned layer') is the outermost layer of the epidermis. Consisting of dead tissue, it protects underlying tissue from infection, dehydration, chemicals and mechanical stress. It is composed of 15–20 layers of flattened cells with no nuclei and cell organelles.
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. In structure, it consists of a keratinized stratified squamous epithelium; four types of cells: keratinocytes, melanocytes, Merkel cells, and Langerhans cells.
Histologic image showing a section of epidermis. Stratum basale labeled near bottom. The stratum basale (basal layer, sometimes referred to as stratum germinativum) is the deepest layer of the five layers of the epidermis, the external covering of skin in mammals. The stratum basale is a single layer of columnar or cuboidal basal cells.
They are present in all layers of the epidermis and are most prominent in the stratum spinosum. [4] They also occur in the papillary dermis , particularly around blood vessels, [ 4 ] as well as in the mucosa of the mouth , foreskin , and vaginal epithelium . [ 5 ]
In addition to its function as a permeability barrier for water and other molecules (prevent water loss), the micro and nano-structure of the cuticle have specialised surface properties that prevent contamination of plant tissues with external water, dirt and microorganisms.