Which of the following layers is NOT one of the three layers of hair?

The epidermis is not one of the three layers of hair and serves a different role entirely. The three actual layers of hair are the cuticle, cortex, and medulla. The cuticle is the outermost layer, composed of flat, overlapping cells that protect the inner layers. The cortex is the thick, middle layer that contains keratin and contributes to the strength and color of the hair. The medulla is the innermost layer, which may be absent in some types of hair but is usually made up of soft, spongy tissue. The epidermis, on the other hand, is part of the skin that covers the body and several hair follicles, but it does not make up the structure of the hair itself. Thus, identifying the epidermis as not being one of the hair layers is accurate and reflects an understanding of hair anatomy.