Final answer:
The hair shaft is composed of three layers: the cuticle, cortex, and medulla. The hair matrix contains a layer of basal cells that are crucial for the growth of the hair shaft.
Step-by-step explanation:
The layers of the hair shaft are cuticle, cortex, and medulla. The cuticle is the outermost layer that provides protection, beneath which is the cortex, forming the main body of the hair shaft and determining its texture. The medulla is the innermost zone and may not be present in all hair types. Additionally, the hair matrix found at the base of the hair follicle contains a layer of basal cells important for hair growth.
Hair growth begins at the hair bulb where the basal cells produce keratinocytes, subsequently forming the hair shaft as they are pushed upward and undergo keratinization. This makes the hair that exits the scalp dead and devoid of sensation. The hair shaft's cuticle, cortex, and medulla are crucial in defining the hair's texture and overall characteristics.