What term refers to the outer layer of the hair?

The term that refers to the outer layer of the hair is the cuticle. The cuticle is a protective layer that consists of overlapping cells, much like shingles on a roof. Its primary function is to protect the inner layers of the hair shaft, particularly the cortex, which is responsible for the hair's strength and color. The cuticle plays a crucial role in maintaining the overall health and appearance of the hair by preventing damage and moisture loss.

Understanding the structure of hair is essential in the field of electrology and hair removal, as it informs practitioners about the hair's characteristics and treatments. The cortex is the middle layer responsible for the bulk and strength of the hair, while the medulla is the innermost layer, which can be present in some types of hair and absent in others. Folate, on the other hand, is not related to hair structure; it refers to a B vitamin important for cell division and metabolism but has no direct connection to the anatomy of hair. This clarity about the cuticle's role reinforces why it is correctly identified as the outer layer of the hair.