American Academy of Professional Coders (AAPC) Practice Exam

The hair shaft is composed of keratin in how many layers?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 3

The hair shaft is indeed composed of keratin in three distinct layers, which are crucial for its structure and function. These layers consist of: 1. **Cuticle**: The outermost layer, which is made up of overlapping, flat, scale-like cells. Its primary role is to protect the inner layers and provides shine and smoothness to the hair. 2. **Cortex**: This middle layer, which forms the bulk of the hair's structure, contains elongated cells filled with keratin. The cortex is responsible for the hair's strength, elasticity, and color, as it contains melanin pigments that provide pigmentation. 3. **Medulla**: The innermost layer, which is not always present in all hair types, particularly in finer hair. The medulla consists of soft, less compact keratinized cells and is thought to play a minor role in the overall structure of the hair. Understanding these layers is essential for various fields, including hair care, cosmetology, and dermatology, as they significantly influence the properties of hair. The distinction between these layers highlights the complexity of hair composition and the significance of keratin in providing the necessary structure and resilience.