New Jersey State Board Esthetics Practice Exam

What is the stratum corneum primarily composed of?

1. Fibroblasts

2. Melanocytes

3. Keratininocytes

4. Adipocytes

The correct answer is: Keratininocytes

The stratum corneum, which is the outermost layer of the epidermis, is primarily composed of keratinocytes. These cells play a crucial role in the skin's barrier function and are responsible for producing keratin, a fibrous protein that helps protect the skin from environmental damage. In the stratum corneum, keratinocytes lose their nucleus and organelles during the process of keratinization, resulting in a tough, protective layer that helps to prevent water loss and shield underlying tissues from pathogens and irritants. Understanding the primary role of keratinocytes is essential for recognizing how the skin maintains its integrity and functions as a protective barrier. Other cells mentioned in the options, such as fibroblasts, melanocytes, and adipocytes, play different roles in the skin but do not primarily compose the stratum corneum. Fibroblasts are mainly found in the dermis and are responsible for producing collagen and elastin, while melanocytes are involved in the production of melanin in the epidermis, contributing to skin pigmentation. Adipocytes are fat cells located in the subcutaneous layer and serve to store energy and provide insulation, but they are not involved in the structure of the stratum corneum itself.