What is the outermost layer of the hair shaft called?

The outermost layer of the hair shaft is called the cuticle. This layer is critical in protecting the inner structures of the hair, particularly the cortex and medulla. The cuticle consists of overlapping, transparent cells that are akin to roof shingles, which help to prevent damage and moisture loss from the hair. This protective barrier plays a significant role in the overall health and appearance of hair, as it can influence shine, smoothness, and susceptibility to damage from environmental factors and hair care practices.

Understanding the function of the cuticle is vital in hair care, as it helps professionals and individuals to choose appropriate hair treatments and products aimed at maintaining the integrity of the hair structure.