New York State Cosmetology Practice Exam 2026 - Free Cosmetology Practice Questions and Study Guide

The epidermis is the outermost layer of the skin and serves as the primary protective barrier. It is composed of several layers of cells, primarily keratinocytes, which produce keratin, a protein that helps waterproof the skin and protect against environmental damage. The epidermis also contains melanocytes, which produce melanin and provide protection against ultraviolet radiation.

This layer is crucial not only for physical protection against pathogens, chemicals, and mechanical injury but also for regulating water loss and maintaining overall skin hydration. The barrier function of the epidermis prevents excessive transepidermal water loss, which is vital for maintaining skin health and integrity.

The dermis, while also important for skin structure and support, mainly contains blood vessels, nerves, hair follicles, and connective tissue, and is not primarily responsible for the barrier function. The subcutaneous layer, or hypodermis, serves as insulation and energy storage and does not play a direct role in protecting the skin's surface.