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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 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 skin (integument) is a composite organ, made up of at least two major layers of tissue: the epidermis and the dermis. [2] The epidermis is the outermost layer, providing the initial barrier to the external environment. It is separated from the dermis by the basement membrane (basal lamina and reticular lamina).
Epidermal stem cells reside in the lower part of the epidermis (stratum basale) and are attached to the basement membrane through hemidesmosomes. Epidermal stem cells divide in a random manner yielding either more stem cells or transit amplifying cells. [ 4 ]
The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. [8] Nourishment is provided to these layers by diffusion from the dermis since the epidermis is without direct blood supply.
Abrasions on elbow and lower arm. The elbow wound will produce a permanent scar. A first-degree abrasion involves only epidermal injury. A second-degree abrasion involves the epidermis as well as the dermis and may bleed slightly. A third-degree abrasion involves damage to the subcutaneous layer and the skin and is often called an avulsion.
The epidermis serves several functions: protection against water loss by way of transpiration, regulation of gas exchange and secretion of metabolic compounds. Most leaves show dorsoventral anatomy: The upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions.