Final answer:
Each individual cuticle scale of the hair is attached to the cortex, which is the middle layer of keratinocytes in the hair follicle.
Step-by-step explanation:
A lengthwise section of hair shows that cuticle scales overlap, and each individual cuticle scale is attached to the cortex. The cortex in hair refers to the second or middle layer of keratinocytes that originate from the hair matrix, which is observed in a cross-section of the hair bulb. The cuticle is the outermost layer of keratinocytes and serves as the protective layer for the underlying cortex. The hair shaft itself has three zones: the cuticle, the cortex, and the medulla, with the medulla forming the central core
The hair matrix contains a layer of basal cells that differentiate into cells that form the hair shaft. Hair growth is a result of these cells dividing and pushing outward, expanding the hair root and shaft. The process of keratinization is completed as these cells are pushed to the skin surface, thereby forming the hair shaft that is externally visible.