Final answer:
The outer covering of the hair shaft is called the cuticle, which is the outermost layer of keratinocytes from the hair matrix. It exists alongside the cortex and medulla, which make up the inner structure of the hair shaft. The hair matrix contains basal cells that are crucial for hair growth.
Step-by-step explanation:
The outer covering of the hair shaft made up of overlapping layers of transparent scales is called the cuticle. A hair shaft has three zones: the outermost zone called the cuticle; the middle zone called the cortex, and the innermost zone called the medulla. The cuticle is the outermost layer of keratinocytes originating from the hair matrix and serves as the protective layer for the inner structures of the hair shaft.
The hair matrix itself contains a layer of basal cells, which are mitotically active and responsible for producing the cells that form the hair shaft. The basal cells of the hair matrix divide and push cells outward in the hair root and shaft as the hair grows. This layer is distinct from the hair follicle, the hair shaft itself, and the glassy membrane.