This is a cross section through part of a hair follicle. The hair follicle comprises of several layers of epithelial cells. The shaft of hair comprises the medulla, cortex and cuticle. The medulla does not always extend the entire length of hair. The cortex will become keratinized and consitute the bulk of shaft. The cells of the cuticle will fill with keratin and eventually lose their nuclei. The cells of the outer root sheath are continuous with the epidermis, whereas the cells of the inner root sheath only extend up to where the sebaceous gland enters the hair follicle. The dermal papilla is an invagination of the underlying dermis. The epithelial cells surrounding the dermal papilla are called the matrix and give rise to the cells of the hair shaft and root sheath.