Which layer of the hair serves as protective armor for the inner layers?

The cuticle is the layer of the hair that serves as protective armor for the inner layers. It is composed of overlapping scale-like cells that fit tightly together and create a barrier against environmental damage, heat, and chemical exposure. This protective layer plays a crucial role in maintaining the integrity and health of the hair shaft.

The cortex, while an important layer that provides strength, elasticity, and color to the hair, does not serve the primary function of protecting the inner layers. The medulla is typically a soft, spongy core that is present in some, but not all, hair types, and it does not have a protective role. The dermis is a layer of skin that contains hair follicles but is not part of the hair structure itself. Thus, the cuticle is correctly identified as the protective outer layer of the hair.