What structural layer of hair protects it from damage?

The cuticle is the outermost layer of the hair shaft, and its primary function is to provide protection against external damage. It consists of overlapping, scale-like cells that help to seal in moisture and protect the underlying layers of the hair, such as the cortex, from environmental factors like pollution, heat, and chemical treatments.

The cuticle's structure allows it to act as a physical barrier while also helping to maintain the integrity of the hair. When the cuticle is intact and healthy, it can prevent damage and keep the hair looking smooth and shiny. If the cuticle becomes damaged or lifted, it can lead to issues such as frizz, split ends, and overall deterioration of the hair’s quality.

In contrast, while the cortex provides strength and color to the hair and the medulla, when present, adds thickness, neither of these layers primarily serves the protective function attributed to the cuticle. The follicle, though important for hair growth, is not part of the hair shaft itself and therefore does not directly protect the hair from damage.