The shape of the hair strand is determined by the shape of the?

The shape of the hair strand is determined by the shape of the hair follicle. Hair follicles are the structures in the skin that produce hair, and their shape can influence whether the hair is straight, wavy, or curly. For instance, a round follicle typically produces straight hair, while an oval or flattened follicle tends to result in curly hair, as the hair strand's cross-section reflects the follicle’s shape.

The other components such as the cuticle layer, inner root sheath, and outer root sheath play essential roles in the health, growth, and structure of the hair, but they do not determine the fundamental shape of the hair strand itself. The cuticle layer protects the hair shaft, while the inner and outer root sheaths are involved in the nourishment and growth of the hair. However, the defining factor for the hair's shape lies in the follicle's configuration.