Epidermis
outer layer of cells of the root, stem or leaf
The epidermis is the outermost layer of the skin and is composed of several layers of different types of cells. It serves as a protective barrier between the body and the environment and plays a crucial role in regulating hydration and body temperature.
The epidermis is made up of five distinct layers, starting with the outermost layer called the stratum corneum, followed by the stratum lucidum, stratum granulosum, stratum spinosum, and finally the basal layer or stratum basale.
The stratum corneum is composed of dead skin cells, called keratinocytes, that provide protection against external insults like UV radiation, chemicals, and infectious agents. The stratum lucidum is a translucent layer that is only present in thick skin, such as the palms and soles of the feet.
The stratum granulosum is responsible for producing lipids that help to form a water-resistant barrier in the skin. The stratum spinosum is where keratinocytes are produced and begin to differentiate into the various epidermal cells types. The basal layer is the deepest layer of the epidermis and is made up of stem cells that continuously divide and give rise to keratinocytes.
Overall, the epidermis plays a crucial role in protecting the body from external insults, regulating water loss, and maintaining homeostasis.
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