American Academy of Professional Coders (AAPC) Practice Exam

What is the stratum corneum primarily composed of?

1. Living cells

2. Soft tissues

3. Horny layers, outermost layer

4. Blood vessels

The correct answer is: Horny layers, outermost layer

The stratum corneum is primarily composed of the horny layers, which constitute the outermost part of the epidermis. This layer is made up of dead skin cells that are rich in keratin, a protein that provides strength and water resistance. These dead cells form a protective barrier that helps prevent water loss and shields underlying tissues from environmental damage such as pathogens, chemicals, and physical abrasions. The other options do not accurately reflect the composition of the stratum corneum. Living cells are found in deeper layers of the epidermis, while blood vessels are located in the dermis, beneath the epidermis. Soft tissues generally refer to various types of flexible tissues in the body but do not specifically describe the structure or composition of the stratum corneum.