naskórka

Naskórek, also known as the epidermis, is the outermost layer of the skin in vertebrates. It serves as a protective barrier against environmental factors, including pathogens, UV radiation, and dehydration. The epidermis is primarily composed of keratinocytes, which are cells that produce keratin, a tough, fibrous protein. These cells are constantly regenerating, with new cells produced in the basal layer and migrating outwards to the surface, where they eventually shed.

The epidermis is avascular, meaning it does not contain blood vessels. It receives nutrients and oxygen through diffusion from the underlying dermis. Within the epidermis, other specialized cells also reside, such as melanocytes, which produce melanin, the pigment responsible for skin color and UV protection, and Langerhans cells, which play a role in the immune system.

The epidermis itself is divided into several layers, each with distinct functions. From deepest to outermost, these are the stratum basale (basal layer), stratum spinosum (spiny layer), stratum granulosum (granular layer), stratum lucidum (clear layer, present only in thick skin like palms and soles), and stratum corneum (horny layer). The stratum corneum, the outermost layer, consists of flattened, dead keratinocytes that form a tough, protective shield. The continuous shedding and renewal of these cells contribute to the skin's resilience and ability to heal. The thickness of the epidermis varies across the body, being thinnest on the eyelids and thickest on the palms and soles.