Epidermës

Epidermës is the outermost layer of skin in vertebrates. It is a stratified squamous epithelium that serves as a protective barrier against the environment, preventing water loss and protecting against pathogens and mechanical damage. The epidermis is avascular, meaning it does not contain blood vessels, and receives nutrients through diffusion from the underlying dermis.

The epidermis is composed of several layers, each with distinct cell types and functions. The deepest layer is the stratum basale, where new keratinocytes are produced through cell division. These cells then migrate upwards through the stratum spinosum, stratum granulosum, and stratum lucidum (present only in thick skin like palms and soles), eventually reaching the outermost stratum corneum. The cells in the stratum corneum are dead, flattened, and filled with keratin, forming a tough, waterproof layer. Melanocytes, responsible for producing melanin pigment, are also found in the stratum basale. Merkel cells, sensory receptors, are also located in this layer.

The epidermis undergoes constant renewal, with cells from the stratum basale migrating to the surface and being shed approximately every 28 days. This continuous shedding helps to remove damaged cells and pathogens. The thickness and structure of the epidermis can vary depending on location on the body and external factors such as sun exposure and friction.