Certified Medical Assistant (CMA) National Credential Practice Test 2025 - Free CMA Practice Questions and Study Guide

Keratinocytes comprise the majority of the epidermis, making up about 90% of its cells. These cells originate from the basal layer of the epidermis and undergo a process called keratinization, where they gradually move toward the surface and eventually die, forming a tough, protective layer of dead cells that help prevent water loss and protect against environmental damage.

Keratinocytes play a crucial role in forming a barrier against pathogens and external stressors, highlighting their importance in skin health and integrity. The other cell types have different functions: melanocytes are responsible for producing melanin, which gives skin its color and protects against UV radiation; fibroblasts are found in the dermis and are involved in the production of collagen and elastin, contributing to skin's structure; and macrophages, which are also located in the dermis, are part of the immune system and help fight infections. These roles are essential but do not involve the main structural component of the epidermis itself, which is primarily made up of keratinocytes.