Which layer of hair is known to be fine or fragile when missing?

The medulla, which is the innermost layer of the hair shaft, plays a crucial role in the overall structure of the hair. Although the medulla is not always present in every hair type, its absence can indicate a finer or more fragile hair quality. When the medulla is missing, hair strength may be diminished, making it more susceptible to damage and breakage.

Both the cuticle and cortex are important for protecting and maintaining the health of the hair; the cuticle serves as the outer protective layer, while the cortex provides the hair's strength and color. The follicle, on the other hand, is not a layer of hair but rather the structure from which hair grows. Each of these components serves distinct functions, but the medulla's connection to hair fineness makes it particularly significant in this context.