Final answer:
The three major layers of the hair are the medulla, cortex, and the cuticle. The cuticle is the outermost protective layer, while the cortex determines hair texture and strength. The hair matrix, from which they originate, contains a layer of basal cells responsible for hair growth.
Step-by-step explanation:
The hair is an interesting structure with different layers that each serve specific functions. The outermost layer of the hair is called the cuticle, which is comprised of very hard, keratinized cells that protect the hair. The middle layer is the cortex, which is made up of compressed, keratinized cells that influence the hair's texture and strength. The innermost layer, present in some but not all types of hair, is the medulla. The cortex and the cuticle originate from the hair matrix, a layer of basal cells that constantly divide to push cells outward, forming the hair shaft.
The hair matrix indeed contains a layer of basal cells (d), which are responsible for producing keratinocytes. These keratinocytes move up the hair bulb, leading to hair growth and ultimately forming the hair that we see. The basal cells' activity and the shape of the hair follicle define the texture and shape of the resulting hair.