The central core of the hair shaft, which is sometimes missing in fine or very fine hair, is the:

• A. Follicle
• B. Cuticle
• C. Cortex
• D. Medulla

Answer: (D)

Verified step by step guidance

1. Understand the structure of the hair shaft, which consists of three main layers: the medulla, cortex, and cuticle.
2. Learn that the medulla is the innermost layer of the hair shaft and is sometimes absent in fine or very fine hair.
3. Recognize that the cortex is the middle layer of the hair shaft, responsible for strength, texture, and color, but it is not the central core.
4. Note that the cuticle is the outermost layer of the hair shaft, providing protection, but it is not the central core either.
5. Conclude that the central core of the hair shaft, which may be missing in fine or very fine hair, is the medulla.