Final answer:
The soft core of a hair is the medulla, surrounded by the cortex, which is the second layer of the hair. The cortex is responsible for hair's texture and surrounds the medulla in the hair shaft.
Step-by-step explanation:
The structure of a hair shaft consists of three main zones: the outermost cuticle, the middle cortex, and the innermost medulla. The medulla is the soft core at the center of the hair, surrounded by the cortex, which is a layer of densely packed, keratinized cells. The cuticle, forming the outer layer, acts as a protective shield for the hair.
The cortex, being the second or middle layer, is crucial in determining hair texture, whether it is straight, wavy, or curly. The shape and structure of the cortex play a pivotal role in defining the overall appearance and characteristics of the hair. The arrangement of keratinocytes within the cortex contributes to the flexibility, strength, and elasticity of the hair shaft.
The hair growth process begins at the hair bulb, situated within the hair follicle. The hair matrix, present in the cross-section of the hair bulb, is responsible for generating new keratinocytes. As these cells are produced by the basal cells of the hair matrix, they move outward, forming the hair shaft. The continuous production and outward movement of keratinocytes contribute to the elongation of the hair shaft.
Understanding the composition and growth process of hair is essential not only for cosmetic reasons but also in the fields of dermatology and forensics. Changes in hair structure can reflect various health conditions, and the analysis of hair shafts can provide valuable information in forensic investigations. The intricate interplay of the medulla, cortex, and cuticle showcases the complexity of hair anatomy and physiology.