Final answer:
The cortex is the middle layer of the hair, located beneath the cuticle layer. It provides the hair's mechanical strength and texture, while the cuticle acts as a protective barrier.
Step-by-step explanation:
The cortex in hair is the middle layer of the hair, located directly beneath the cuticle layer. The cortex is the second or middle layer of keratinocytes originating from the hair matrix, as observed in a cross-section of the hair bulb. The cuticle, on the other hand, is the outermost layer of keratinocytes originating from the hair matrix. The hair shaft itself is composed of dead, keratinized cells and is considered to be without any biochemical activity.
The cortex is responsible for the majority of the hair's mechanical strength and its texture. It also holds the melanin that gives hair its color. The cuticle layer serves as a protective barrier for the inner layers of the hair. Understanding the structure of the hair, including these layers, is crucial for fields such as dermatology and cosmetology.