Hair shaft layers

These 3 concentric layers are formed by the germinal matrix. The cell borders are indistinct, however, and cross sections through hair follicles near the skin surface often do not show the cellular nature of these layers. In addition, the hair itself may be dislodged from the canal during tissue processing, leaving only the open space (follicular canal) originally occupied by the shaft. The medulla forms the shaft's thin central core. It is composed of poorly keratinized and often vacuolated cells. The cortex surrounds the medulla and is composed of several layers of well-keratinized polygonal cells. The cuticle is the shaft's outermost layer. Within the bulb, its cells are cuboidal; farther up the shaft they become tall columnar, fill with keratin, and finally change their orientation to become a few layers of flattened, highly keratinized cells. These cells form the hard, shinglelike cuticle that covers the hair's outer surface.