The epidermis is the superficial layer of the skin. Its thickness varies depending on the location, being thicker in areas exposed to frequent friction such as the palms and soles, and thinner in areas like the eyelids. It is composed of stratified, keratinized, squamous, and non-vascularized epithelial tissue. The epidermis covers the dermis, which is highly vascularized and ensures its nutrition by diffusion, as the epidermis itself lacks blood vessels. Embryologically, the epidermis originates from the ectoderm, the outermost layer of the embryo.

Constituents of the Epidermis

The main constituents of the epidermis are keratinocytes, representing about 80% of its cell population. Keratinocytes produce keratins, structural proteins critical for maintaining skin integrity, strength, and barrier function. These cells undergo a tightly regulated process of proliferation in the basal layer, followed by differentiation as they migrate upward through the layers of the epidermis, culminating in the formation of the stratum corneum — the outermost layer of dead, flattened cells that are continuously shed through desquamation.

Other key cells in the epidermis include:

• Melanocytes: Produce melanin pigment, protecting underlying tissues from ultraviolet radiation and contributing to skin color.
• Langerhans Cells: Immunocompetent dendritic cells involved in immune surveillance, capturing and presenting antigens to T lymphocytes.
• Merkel Cells: Specialized mechanoreceptors responsible for the sensation of touch and pressure.