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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 epidermis 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 .
Histologic image showing a section of epidermis. Stratum spinosum labeled slightly below center. The stratum spinosum (or spinous layer/prickle cell layer) [1] is a layer of the epidermis found between the stratum granulosum and stratum basale. [2] This layer is composed of polyhedral keratinocytes. [3] [4] These are joined with desmosomes. [3]
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.
Earth is the only place in the universe known to harbor life, where it exists in multiple environments. [8] [9] The origin of life on Earth was at least 3.5 billion years ago, possibly as early as 3.8-4.1 billion years ago. [2] [3] [4] Since its emergence, life has persisted in several geological environments.
For example, the expression of N-cadherin is crucial to maintaining separation of precursor neural cells from precursor epithelial cells. [2] Likewise, while the surface ectoderm becomes the epidermis , [ 6 ] the neuroectoderm is induced along the neural pathway by the notochord , which is typically positioned above it.
In 2012, a 508 million year old species of annelid found near the Burgess shale beds in British Columbia, Kootenayscolex, was found that changed the hypotheses about how the annelid head developed. It appears to have bristles on its head segment akin to those along its body, as if the head simply developed as a specialized version of a ...
An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial ) tissues line the outer surfaces of many internal organs , the corresponding inner surfaces of body cavities , and the inner surfaces of blood vessels .
As the epidermis of the plant is covered with water barriers such as lignin and waxy cuticles, the night opening of the stomata is the main channel for water movement for xerophytes in arid conditions. [12] Even when water is not scarce, the xerophytes A. Americana and pineapple plant are found to utilise water more efficiently than mesophytes ...