húðþekjunni

Húðþekjan is the outermost layer of the skin in humans and other vertebrates. It serves as a primary barrier against the environment, protecting the body from physical damage, pathogens, and dehydration. This stratified squamous epithelium is composed of several distinct layers, each with specific functions. The deepest layer, the stratum basale, is where new skin cells, called keratinocytes, are produced through cell division. As these cells mature, they move upwards through the strata, undergoing a process called keratinization. During this process, they fill with a tough protein called keratin and eventually die. The outermost layer, the stratum corneum, consists of flattened, dead keratinocytes that are continuously shed and replaced.

The epidermis also contains other specialized cells. Melanocytes, located in the stratum basale, produce melanin, the pigment responsible for skin color and protection against ultraviolet radiation. Merkel cells, also found in the stratum basale, are sensory receptors involved in light touch. Langerhans cells, a type of immune cell, reside in the stratum spinosum and play a role in the skin's immune defense. The thickness of the epidermis varies across the body, being generally thicker in areas subject to more friction, such as the soles of the feet and palms of the hands. Overall, the epidermis is a dynamic and crucial organ for maintaining homeostasis and protecting the organism.