Search results
Results from the WOW.Com Content Network
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 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). The epidermis contains melanocytes and gives color to the skin. The deepest layer of the epidermis also contains nerve endings.
Skin secretions originate from glands that in dermal layer of the epidermis. Sweat, a physiological aid to body temperature regulation, is secreted by eccrine glands. Sebaceous glands secrete the skin lubricant sebum. Sebum is secreted onto the hair shaft and it prevents the hair from splitting. It consists mostly of lipids.
Melanocytes are ideally positioned in the epidermis to be sentinels against harmful pathogens. They reside in the stratum basale, [23] the lowest layer of the epidermis, but they use their dendrites to interact with cells in other layers, [24] and to capture pathogens that enter the epidermis. [21]
Within the healed epidermis they will be replaced by keratinocytes originating from the epidermis. [29] [30] At the opposite, epidermal keratinocytes, can contribute to de novo hair follicle formation during the healing of large wounds. [31] Functional keratinocytes are needed for tympanic perforation healing. [32]
These cells contain organelles called Birbeck granules. 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]