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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, "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 epidermis is the outermost cell layer of the primary plant body. In some older works the cells of the leaf epidermis have been regarded as specialized parenchyma cells, [1] but the established modern preference has long been to classify the epidermis as dermal tissue, [2] whereas parenchyma is classified as ground tissue. [3]
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.
The primary function of the plant cuticle is as a water permeability barrier that prevents evaporation of water from the epidermal surface, and also prevents external water and solutes from entering the tissues. [11]
Insensible perspiration, also known as transepidermal water loss, is the passive vapour diffusion of water through the epidermis. Insensible perspiration takes place at an almost constant rate and reflects evaporative loss from the epithelial cells of the skin. [1] Unlike sweating, the lost fluid is pure without additional solutes. For this ...
The homeostasis function is regulated by the calcium gradient in the epidermis. [17] Usually the calcium level is very low in stratum corneum, but high in stratum granulosum. Once the permeability barrier is disrupted an influx of water occurs in the stratum corneum, which in turn increases the calcium levels in the stratum corneum but ...
This hyperpolarization of the membrane allowed the accumulation of charged potassium (K +) ions and chloride (Cl −) ions, which in turn, increases the solute concentration causing the water potential to decrease. The negative water potential allows for osmosis to occur in the guard cell, so that water enters, allowing the cell to become turgid.